Thermal management of fuel cell units and systems

ABSTRACT

Various designs and configurations of and methods of operating fuel cell units, fuel cell systems and combined heat and power systems are provided that permit efficient thermal management of such units and systems to improve their operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 17/244,248, filed on Apr. 29, 2021, whichapplication is a divisional patent application of U.S. patentapplication Ser. No. 15/350,539, filed on Nov. 14, 2016, which is acontinuation of International Application No. PCT/US2015/051209, filedon Sep. 21, 2015, which claims priority to and the benefit of U.S.Patent Application No. 62/052,706, filed on Sep. 19, 2014, each of whichis incorporated by reference herein in its entirety.

FIELD

The present teachings relate generally to fuel cell units and systems.More particularly, the present teachings related to the thermalmanagement of a fuel cell unit and a fuel cell system.

BACKGROUND

Thermal management of a fuel cell system or a combined heat and power(“CHP”) system (which can include one or more fuel cell units) is animportant consideration in their design for efficient operation andgeneration of electricity and/or heat. To manage thermally fuel cellsystems, air flow typically is used to move heated air and other fluidsthrough a fuel cell unit and the system including through the vents ofthe fuel cells stacks. However, the use of air flow to manage thermallya fuel cell system can create undesirable pressure drops and associatedfluid flow distribution anomalies throughout the system, impacting itsoperation.

In the case of a fuel cell system where a plurality of fuel cell stacksare present and aligned in an array, cool air frequently is deliveredlinearly across the array from one end to the other to assist incontrolling the temperature of the fuel cell stacks. However, in such anarrangement, although the first fuel cell units in the array can besufficiently cooled or temperature-regulated, often the fuel cell unitsthat are last to experience the “cool” air are insufficientlytemperature-regulated as the delivered air is heated as it moves throughthe system and become ineffective in regulating the temperature of thelatter fuel cell units, where current collection and othertemperature-sensitive structure or electronics may be located. Moreover,such a configuration in operation can cause variable temperatures withinthe system, for example, producing “hot spots” and/or “cold spots,” asair flow is increased to attempt to compensate for the lack of thermalcontrol.

In addition, air exhaust streams from fuel cells and/or heaters oftentransfer the heat of the exhausted gas to circulating water via a heatexchanger to effect gas-to-liquid heat transfer. In such a case, the airexhaust stream typically needs to be diluted to reduce its temperatureto avoid boiling the water in the exhaust stream.

Thus, for more efficient and consistent operation of a fuel cell or CHPsystem, the art desires new designs and configurations of fuel cellunits and fuel cell and CHP systems and methods of operating such unitsand systems that can manage better and more efficiently the thermalenvironment around a fuel cell unit and/or within a fuel cell or CHPsystem.

SUMMARY

The present teachings provide fuel cell units, fuel cell systems, andfuel cell units as or integrated into CHP systems as well as methods ofthermally managing such units and systems that can address variousdeficiencies and shortcomings of the state-of-the-art, including thoseoutlined above. More specifically, the design and configuration of fuelcell units, fuel cell systems, and CHP systems including fuel cellunit(s) and practice of the methods according to the present teachingscan permit more efficient thermal management of fuel cell unitsincluding those in a fuel cell system or a CHP system.

For example, one feature of the present teachings is that individualfuel cell units of a fuel cell system can be within a thermally-shieldedzone. Each thermally-shielded zone can include a temperature-regulatingfluid inlet and one or more exhaust fluid outlets, thereby permittingindependent monitoring and management of the thermal environment foreach fuel cell unit for increased control of a fuel cell system. Asource of positive gaseous pressure such as a fan or blower can be inoperable fluid communication with a temperature-regulating fluid inletto facilitate movement and heat transfer within a thermally-shieldedzone. In such arrangements, a fuel cell unit can be cooled more quicklyand efficiently. Moreover, the fuel cell or CHP system can have asmaller footprint or package because the fuel cell units and/or theheater units are not uncontrollably radiating heat outward.

Another feature is that a fuel cell system of the present teachings canbe designed to take advantage of the heat from the exhaust from a fuelcell unit. When heated exhaust fluids are released within athermally-shielded zone, the heat can be used for heating the componentsof the fuel cell unit within the thermally-shielded zone. For example, afuel cell unit can have a vaporizer located within a thermally-shieldedzone and the heat of the exhaust fluids within the thermally-shieldedzone can assist in preheating liquid reformable fuels and fluid streamsprior to introduction to the vaporizer as well as to assist inmaintaining the operating temperature of the vaporizer. Where the heatedexhaust fluids are released outside of a thermally-shielded zone, theexhaust streams from two or more fuel cell units can be combined, forexample, pointed at each other, and used for heating other components ofthe fuel cell or CHP system such as those components present between thethermally-shielded zones of the fuel cell units. In other words, theheated exhaust fluids can be combined and create a heated zone betweenthe two or more fuel cell units. Moreover, heated exhaust fluids can becontacted with a liquid heat-exchange plate or a liquid heat-exchangejacket associated with a fuel cell unit or system to capture and controlthe thermal environment.

Yet another feature is that a fuel cell unit of the present teachingscan be designed to transfer preferentially heat through and/or from atleast one face, or segments of a face, or one surface of the fuel cellunit, where a reduced level of thermal insulation can be in contactwith, adjacent to, and/or in thermal communication with the at least oneface or segment thereof or one surface of the fuel cell unit. Aretaining structure can secure the thermal insulation including reducedlevels of thermal insulation about the fuel cell unit as needed. Theretaining structure typically is a thermally conductive material and canbe in the form of a sheet such as a metal sheet or “sheet metal.” Theretaining structure can be or include a carbon fiber. A fuel cell unitincluding thermal insulation and/or a retaining structure can be locatedin a thermally-regulated zone or a thermally-shielded zone. In similarfashion, more than one face or segment thereof or one surface of a fuelcell unit or a thermally-regulated zone can be associated with a reducedlevel of thermal insulation.

Likewise, an array of fuel cells and/or thermally-regulated zones canhave one or more of their faces or segments thereof or surfacesassociated with a reduced level of thermal insulation to transfer heatpreferentially among the array of fuel cell units. For example, heatfrom two or more fuel cell units and/or thermally-regulated zones can bepreferentially transferred towards each other or among the fuel cellunits and/or thermally-regulated zones to create a heated zone betweenor among the units and/or zones. The thermal insulation can includesolid thermal insulation and/or fluid thermal insulation. Athermally-regulated zone can include a temperature-regulating fluidinlet and one or more exhaust outlets. A source of positive gas pressurecan be in operable fluid communication with the temperature-regulatingfluid inlet(s) and one or more of a reformer, a fuel cell stack, and anafterburner.

Still another feature of the present teachings is that one or morecomponents of a fuel cell unit such as a fuel cell stack and/or anafterburner can be in thermal communication with a liquid heat-exchangeplate or a liquid heat-exchange jacket to facilitate heat transfer fromthese components of a fuel cell unit and assist in its thermalmanagement and that of the fuel cell system. In particular embodiments,a liquid heat-exchange jacket or a liquid heat-exchange plate can be aretaining structure for the fuel cell unit and its associated thermalinsulation. For example, the thermal insulation such as a reduced levelof thermal insulation can be in contact with a liquid heat-exchangejacket or a liquid heat-exchange plate.

An additional feature and benefit of the present teachings is that theheated heat-exchange liquid exiting the liquid heat-exchange plate orthe liquid heat-exchange jacket can be routed or delivered for a varietyof purposes and can conserve the energy of the system for efficient use.As one example, using a liquid heat-exchange plate or a liquidheat-exchange jacket to cool a fuel cell unit can permit a reducedamount of or less cathode air to be flowed or delivered through thesystem as the exhaust streams can be cooler and require less dilution.

In addition, a combination of features of the present teachings caninclude a liquid heat-exchange plate or a liquid heat-exchange jacketassociated with, for example, in thermal communication with, one or morefaces or surfaces of a fuel cell unit associated with a reduced level ofthermal insulation, thereby to transfer preferentially heat from thefuel cell unit (from or through the one or more faces or surfacesassociated with a reduced level of thermal insulation) to theheat-exchange liquid. Such an arrangement as well as others describedherein can permit heat sensitive components and structure such aselectronics and balance of plant components to be located in lowertemperature (cooler) zones of the fuel cell or CHP system.

Other features of the present teachings include a common (reformable)fuel source conduit permitting multiple fuel cell units, for example,their reformers and/or vaporizers, to be connected or coupled thereto,and/or a common liquid heat-exchange conduit, permitting multipleheat-exchange plates or jackets of individual fuel cell units to beconnected or coupled thereto. In such a design, fuel cell units can beinterchanged readily in a multi-fuel cell unit system or a CHP system,including interchangeable heater unit(s). Moreover, the valveassemblies, sensor assemblies, and/or control system including acontroller can be in communication among each other to control logicallythe flow path of fluids individually for each fuel cell unit and/orheater unit of a fuel cell system and/or CHP system as desired for aparticular application, which can include start-up and shut-down modesas well as the coupling and decoupling of a fuel cell unit or a heaterunit to a common fuel source conduit and/or a common liquidheat-exchange conduit.

Accordingly, one aspect of the present teachings is a fuel cell systemincluding configurations and/or features that permit more efficientthermal management of the system. In various embodiments, a fuel cellsystem includes one or more fuel cell units, where the fuel cell unitincludes a reformer; a fuel cell stack in operable fluid communicationwith the reformer; and an afterburner in operable fluid communicationwith the fuel cell stack. The fuel cell unit can be within athermally-shielded zone or a thermally-regulated zone. Athermally-shielded zone and a thermally-regulated zone can include atemperature-regulating fluid inlet and one or more exhaust fluidoutlets. A source of positive gaseous pressure such as a fan or blowercan be in operable fluid communication with the temperature-regulatingfluid inlet(s) and one or more of the reformer, the fuel cell stack andthe afterburner.

In various embodiments, a fuel cell system includes one or more fuelcell units including a reformer; a fuel cell stack in operable fluidcommunication with the reformer; an afterburner in operable fluidcommunication with the fuel cell stack; and a vaporizer in thermalcommunication with the afterburner and in operable fluid communicationwith the reformer. The fuel cell unit can be within a thermally-shieldedzone or a thermally-regulated zone, where the thermally-shielded zoneand the thermally-regulated zone include a temperature-regulating fluidinlet and one or more exhaust fluid outlets. A source of positivegaseous pressure can be in operable fluid communication with thetemperature-regulating fluid inlet(s) and one or more of the reformer,the fuel cell stack and the afterburner.

In some embodiments, a fuel cell system of the present teachings caninclude at least a first fuel cell unit and a second fuel cell unit.Each fuel cell unit can include a reformer; a fuel cell stack inoperable fluid communication with the reformer; and an afterburner inoperable fluid communication with the fuel cell stack. Thermalinsulation such as solid thermal insulation and/or fluid thermalinsulation can be distributed about a fuel cell unit. A reduced level ofthermal insulation can be in contact with, adjacent to, and/or inthermal communication with at least one face, or segment thereof, or onesurface of the first fuel cell unit and/or the second fuel cell unit,for example, on or adjacent to at least one of the reformer, the fuelcell stack, and the afterburner of the first fuel cell unit and/or thereformer, the fuel cell stack, and the afterburner of the second fuelcell unit, thereby to increase heat transfer through and/or from the atleast one face, segment thereof, or one surface associated with thereduced level of thermal insulation. A fuel cell unit associated with orhaving a reduce level of thermal insulation can be within athermally-regulated zone or a thermally-shielded zone, where thethermally-regulated zone or the thermally-shielded zone can include oneor more temperature-regulating fluid inlets and one or more exhaustoutlets.

In certain embodiments, each of at least a first fuel cell unit and asecond fuel cell unit independently includes a reformer; a fuel cellstack in operable fluid communication with the reformer; an afterburnerin operable fluid communication with the fuel cell stack; and an exhaustconduit in thermal and operable fluid communication with theafterburner, where the exhaust conduit includes an upstream end and adownstream end. The downstream end of the exhaust conduit of first fuelcell unit can be directed towards the downstream end of the exhaustconduit of the second fuel cell unit whereby the exhaust streams fromeach fuel cell unit can combine, for example, in a channel between thetwo fuel cell units thereby creating a “heated zone.”

In particular embodiments, a fuel cell system of the present teachingscan include a liquid heat-exchange plate or a liquid heat-exchangejacket in thermal communication with one or more of a reformer, a fuelcell stack, and an afterburner of a fuel cell unit or independently afirst fuel cell unit and a second fuel cell unit. A liquid heat-exchangejacket can be in thermal communication with, for example, in contactwith, one or more faces, or segments thereof, or surfaces of one or moreof a reformer, a fuel cell stack, and an afterburner, and/or canencompass and contact, be adjacent to and/or be in thermal communicationwith an exposed perimeter such as a circumference or a partial perimeterof one or more of the reformer, the fuel cell stack, and theafterburner.

In some embodiments, a liquid heat-exchange plate or a liquidheat-exchange jacket can be in thermal communication with at least oneface, or segment thereof, or one surface of a fuel cell unit, such as ofa reformer, a fuel cell stack and/or an afterburner, associated with areduced level of thermal insulation thereby to increase preferentiallyheat transfer to the circulating heat-exchange liquid through and/orfrom the at least one face or one surface associated with the reducedlevel of thermal insulation. The liquid heat-exchange plate or theliquid heat-exchange jacket can be adjacent to one or more of thereformer, the fuel cell stack and/or the afterburner such as being incontact with the thermal insulation, for example, a reduced level ofthermal insulation, in contact with, adjacent to and/or in thermalcommunication with the reformer, the fuel cell stack and/or theafterburner, or being in contact with or adjacent to a retainingstructure of the fuel cell unit. In such an arrangement, thermalinsulation and/or a retaining structure can be between the reformer, thefuel cell stack and/or the afterburner and the liquid heat-exchangeplate or the liquid heat-exchange jacket. A liquid heat-exchange plateor a liquid heat-exchange jacket can include an interface configured toconnect the liquid heat-exchange plate or the liquid heat-exchangejacket to a common liquid heat-exchange conduit of the fuel cell system.

In various embodiments, the present teachings provide a CHP systemincluding a fuel cell system of the present teachings; and a heater unitpositioned adjacent to a fuel cell unit, or at least one of a first fuelcell unit and a second fuel cell unit.

In some embodiments, the fuel cell system or CHP system can include acommon (reformable) fuel source conduit. A common fuel source conduitcan be in operable fluid communication with one or more of a reformerand a vaporizer of a fuel cell unit.

In another aspect, the present teachings provide methods of managingthermally a fuel cell system including a fuel cell unit. In variousembodiments, a method of thermally managing a fuel cell system caninclude delivering temperature-regulating fluids through atemperature-regulating fluid inlet of a thermally-shielded zone or athermally-regulated zone; and exhausting heated exhaust fluids throughone or more exhaust fluid outlets of the thermally-shielded zone or thethermally-regulated zone. The fuel cell unit can be within athermally-shielded zone or a thermally-regulated zone. The heatedexhaust fluids can include heated temperature-regulating fluids. Theheated exhaust fluids can include heated afterburner combustionproducts.

In various embodiments, methods of thermally managing a fuel cell systemcan include exhausting heated fluid, for example, from an exhaustconduit, from a first fuel cell unit towards a second fuel cell unit;and exhausting heated fluid from the second fuel cell unit towards thefirst fuel cell unit. Each of the first fuel cell unit and the secondfuel cell unit independently can be within a thermally-shielded zone ora thermally-regulated zone. For example, the first fuel cell unit can bewithin its own thermally-shielded zone and the second fuel cell unit canbe within its own thermally-shielded zone such that the first fuel cellunit and the second fuel cell unit are thermally-shielded from eachother.

In some embodiments, methods of thermally managing a fuel cell systemcan include transferring heat preferentially from a face or a surface ofa first fuel cell unit, where a reduced level of thermal insulation canbe on, adjacent to, and/or in thermal communication with the face, thesegment thereof, or the surface of the first fuel cell unit thereby toincrease heat transfer through and/or from the face, the segmentthereof, or the surface of the first fuel cell unit associated with thereduced level of thermal insulation. The methods also can includetransferring heat preferentially from a face or a surface of a secondfuel cell unit in a similar fashion. In methods using preferential heattransfer as described herein, one or more of the fuel cell units and/orheater units can be within a thermally-shielded zone or athermally-regulated zone, where the thermally-shielded zone or thethermally-regulated zone includes one or more temperature-regulatingfluid inlets and exhaust fluid outlets.

In certain embodiments, methods of the present teachings can includecirculating a heat-exchange liquid in thermal communication with one ormore of a reformer, a fuel cell stack and an afterburner of a fuel cellunit, or independently a first fuel cell unit and/or a second fuel cellunit, to promote heat transfer from one or more of the reformers, thefuel cell stacks, and the afterburners to the circulating heat-exchangeliquid. The methods can include transferring heat preferentially to thecirculating heat-exchange liquid, for example, from one or more faces orsurfaces of a fuel cell unit associated with a reduced level of thermalinsulation in contact with, adjacent to, and/or in thermal communicationwith the one or more faces or surfaces of the fuel cell unit.Circulating a heat-exchange liquid can include circulating aheat-exchange liquid including water and/or a glycol. The methods caninclude connecting the fuel cell unit, or independently the first fuelcell unit and the second fuel cell unit, to a common liquidheat-exchange conduit of the fuel cell system. The methods can includedelivering heated heat-exchange liquid to one or more of aliquid-to-liquid heat exchanger, a liquid-to-gas heat exchanger, and anair conditioning unit or system.

In particular embodiments, methods of the present teachings can includeconnecting a fuel cell unit and/or a heater unit, or independently thefirst fuel cell unit and the second fuel cell unit, to a common fuelsource conduit of a fuel cell system.

The foregoing as well as other features and advantages of the presentteachings will be more fully understood from the following figures,description, examples, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings described below are forillustration purposes only. Like numerals generally refer to like parts.The drawings are not necessarily to scale, with emphasis generally beingplaced upon illustrating the principles of the present teachings. Thedrawings are not intended to limit the scope of the present teachings inany way.

FIG. 1A is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings where a fuelcell unit is within a thermally-shielded zone and the downstream end ofthe exhaust conduit from the afterburner terminates outside of thethermally-shielded zone.

FIG. 1B is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 1A but the downstreamend of the exhaust conduit from the afterburner terminates within thethermally-shielded zone.

FIG. 1C is a schematic diagram of a top view of an embodiment of a fuelcell system of the present teachings depicting four fuel cell unitssimilar to those of FIG. 1B, but where the anode reactants conduits ofthe fuel cell units are positioned on the opposite side of the fuel cellunit such that the anode reactants conduits are coupled to a common fuelsource conduit.

FIG. 1D is a schematic diagram of a top view of an embodiment of a fuelcell system of the present teachings depicting four fuel cell unitssimilar to those of FIG. 1B, where the cathode air conduits of the fuelcell units are coupled to a common cathode air conduit and the exhaustconduits of adjacent fuel cell units are pointed towards each other andinto a channel formed between the fuel cell units.

FIG. 1E is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings similar toFIG. 1A, but where the fuel cell unit is within a thermally-regulatedzone that has a reduced level of thermal insulation adjacent to asegment of the face of the fuel cell unit having the exhaust conduit.

FIG. 2A is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 1A but the afterburner,fuel cell stack and reformer are in contact with a liquid heat-exchangeplate or a liquid heat-exchange jacket.

FIG. 2B is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 1B but the afterburner,fuel cell stack and reformer are in contact with a liquid heat-exchangeplate or a liquid heat-exchange jacket.

FIG. 2C is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 2B except that only theafterburner and fuel cell stack are in contact with a liquidheat-exchange plate or a liquid heat-exchange jacket where at least twoof the faces of the afterburner and one face of the fuel cell stackinclude a reduced level of thermal insulation for preferential heattransfer to the liquid heat-exchange liquid.

FIG. 2D is a schematic diagram of a top view of an embodiment of a fuelcell system of the present teachings depicting two fuel cell unitssimilar to those of FIG. 2A, but where each liquid heat-exchange plateor liquid heat-exchange jacket is coupled to a common liquidheat-exchange conduit.

FIG. 3 is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings where a fuelcell unit including a vaporizer is within a thermally-shielded zone andthe downstream end of the exhaust conduit from the afterburnerterminates within the thermally-shielded zone.

FIG. 4A is a schematic diagram of a top view of an embodiment of a CHPsystem of the present teachings where the CHP system includes five fuelcell units, a heater unit, a vaporizer in a channel between two fuelcell units, a plurality of sources of positive gaseous pressure to moveand direct the exhaust from the fuel cell units and the heater, and acommon fuel source conduit.

FIG. 4B is a schematic diagram of a side cross-sectional view of twoexemplary fuel cell units of FIG. 4A along the line A-A.

FIGS. 5A-F are schematic diagrams of top views of various configurationsof fuel cell systems of the present teachings. Each fuel cell unit andits thermal insulation is represented by a square or a rectangle, wherethermal insulation is associated with each face or surface around theperimeter of the fuel cell unit within the square or rectangle. A faceor surface of a fuel cell unit associated with a reduced level ofthermal insulation is represented with a thinner line compared to otherfaces or surfaces represented by thicker lines. FIG. 5A depicts a topview of a square horizontal cross-section of a fuel cell unit and itsthermal insulation. FIG. 5B depicts a first fuel cell unit and to itsright hand side, a second fuel cell unit, along with their respectivethermal insulation, where the second fuel cell unit can be within athermally-shielded zone or a thermally-regulated zone so that nopreferential heat transfer occurs from the second fuel cell unit. FIG.5C depicts a first fuel cell unit and a second fuel cell unit, alongwith their respective thermal insulation, where preferential heattransfer can occur from one fuel cell unit towards the other fuel cellunit, and vice versa. FIG. 5D depicts a first fuel cell unit, a secondfuel cell unit, and a third fuel cell unit, along with their respectivethermal insulation, where two faces or surfaces of the middle fuel cellunit can preferentially transfer heat to or receive heat from the othertwo fuel cell units. FIG. 5E depicts a 2×3 array of fuel cell units andtheir respective thermal insulation, where the fuel cell units not onlypreferentially can transfer heat between or among each 1×3 array, butalso preferentially can transfer heat into and across the channel formedby each 1×3 array. FIG. 5F depicts another 2×3 array of fuel cell unitsand their respective thermal insulation, where the heat generated by thefuel cell units can be preferentially transferred outward and away fromthe internal channel between each 1×3 array of fuel cell units.

FIG. 6A is a schematic diagram of a side cross-sectional view of a fuelcell unit having a reduced level of thermal insulation on or adjacent tosegments of two faces of the fuel cell unit. A segment of a face orsurface of a fuel cell unit associated with a reduced level of thermalinsulation is represented with one line compared to other segments of aface or surface represented by three lines.

FIG. 6B is a schematic diagram of a side cross-sectional view of a fuelcell unit similar to FIG. 6A and includes one or more liquidheat-exchange plates or jackets adjacent to surfaces or faces of theafterburner and/or fuel cell stack associated with a reduced level ofthermal insulation.

FIG. 6C is a schematic diagram of a side cross-sectional view of thefuel cell unit of FIG. 6B and includes two afterburner exhaust conduitsin contact with or adjacent to the one or more liquid heat-exchangeplates or jackets for an additional source of heat for the liquidheat-exchange liquid.

FIG. 6D is a schematic diagram of a top view of a fuel cell unitincluding its thermal insulation around the perimeter of the fuel cellunit where the electronics and/or power conditioning components of thefuel cell unit are located on or adjacent a face, a segment thereof, orsurface of the fuel cell unit not having a reduced level of thermalinsulation. A face or surface of a fuel cell unit associated with areduced level of thermal insulation is represented with a thinner linecompared to other faces or surfaces represented by thicker lines.

FIG. 7 is a schematic diagram of a top view of a fuel cell system havingtwo fuel cell units arranged in a horizontal direction from the reformerto the fuel cell stack to the afterburner where the fuel cell unitsshare a common fuel source conduit and the heat and exhaust of the fuelcell units is preferentially transferred in a direction away from theorigination of the common fuel source conduit. A face or surface of afuel cell unit associated with a reduced level of thermal insulation isrepresented with a thinner line compared to other faces or surfacesrepresented by thicker lines.

DETAILED DESCRIPTION

It now has been discovered that the thermal management of a fuel cellunit, a fuel cell system, and a combined heat and power (“CHP”) systemcan be improved by the practice of the present teachings. Morespecifically, the present teachings provide a fuel cell unit withvarious configurations and features that advantageously capture and useheat generated by one or more components of the unit or system and/orpermit the regulation of the environment, for example, the thermalenvironment, around a fuel cell unit and/or within a fuel cell or CHPsystem.

The configurations and designs of fuel cell units and systems of thepresent teachings can increase regulation and control of the thermalenvironment surrounding a fuel cell unit. For example, each individualfuel cell unit in a fuel cell or CHP system can be within athermally-shielded zone such that the thermal environment of each fuelcell can be controlled for efficient operation of each fuel cell unit ofthe system. Such control can be achieved by the use of a source ofpositive gaseous pressure such as a fan or blower in operable fluidcommunication with the interior of the thermally-shielded zone through atemperature-regulating fluid inlet. The source of positive gaseouspressure can be in fluid communication with the interior of thethermally-shielded zone by being present in the thermally-shielded zone(or a thermally-regulated zone), for example, a fan or blower presentand in direct fluid communication with components of a fuel cell unitwithin the zone such that a temperature-regulating fluid inlet isunnecessary.

The thermally-shielded zone can include one or more exhaust fluidoutlets to exhaust heated fluids, for example, including gas passedthrough the temperature-regulating fluid inlet. In operation, thetemperature within a thermally-shielded zone around a fuel cell unit canbe monitored and the flow of gas such as air from the source of positivegaseous pressure can be adjusted to achieve the proper balance of heatcirculation and/or exchange to regulate the temperature around the fuelcell accordingly. The same process can occur independently for each fuelcell unit of the system thereby providing more efficient thermalmanagement of the fuel cell system and addressing certain disadvantagesof the state-of-the-art.

The present teachings can exploit the heat generated during theoperation of a fuel cell unit and use that heat to heat (or preheat) oneor more fluid streams of a fuel cell unit or a fuel cell or CHP system.For example, the generated heat can be used to heat one or more of acathode air stream, an anode reactants or fuel stream, and a liquidreformable fuel, for example, prior to delivery to a vaporizer. Thegenerated heat can be used to maintain vaporized liquid reformable fuelin a gaseous state while being delivered from the vaporizer to areformer. A vaporizer can be present within a thermally-shield zone.Accordingly, the heat generated by a fuel cell unit in thermalcommunication with the vaporizer can assist in heating the vaporizer andthe fluids moving to and from it.

The generated heat can be transferred to a heat-exchange liquid such aswater and/or a glycol, for example, in a liquid heat-exchange plate or aliquid heat-exchange jacket that is in thermal communication with theheat-generating components of a fuel cell unit such as the reformer, thefuel cell stack and/or the afterburner. Where the thermal load of thefuel cell unit is increased, a liquid heat-exchange plate or a liquidheat-exchange jacket can be present on more faces or surfaces of thefuel cell unit, i.e., have increased and more available surface area forheat exchange. The heated heat-exchange liquid can be routed ordelivered to a fluid or hydraulic circuit panel that can direct theheated heat-exchange liquid via one or more flow paths, for example,using a pump, to various devices for various purposes including thefollowing examples as well as others described herein.

First, the heated heat-exchange liquid can be delivered to aliquid-to-liquid heat exchanger or a liquid-to-gas heat exchanger thatcan act as a heat rejection sink or loop to reduce the temperature ofthe heat-exchange liquid and/or assist in maintaining the range oftemperatures appropriate for the heat-exchange liquid. That is, thecirculating heat-exchange liquid can be maintained within a fixedtemperature range, for example, by using a thermostat controllerassociated with this fluid path or circuit along with the appropriateheat exchanger (which may require the addition of heat until the fuelcell unit or system is operating in a steady-state mode). In certainembodiments, particularly those applications having a high thermaloutput, additional thermal insulation can be provided between the fuelcell unit or certain of its components and a liquid heat-exchange plateor a liquid heat-exchange jacket to assist in controlling thetemperature of the heat-exchange liquid to prevent it from reaching itsboiling point.

Second, the heated heat-exchange liquid can be delivered to aliquid-to-liquid heat exchanger such as a water tank to facilitateefficient liquid-to-liquid heat transfer, for example, to providebaseboard heat or to heat other components or materials with the hotwater.

Third, the heated heat-exchange liquid can be delivered to aliquid-to-gas (e.g., liquid-to-air) heat exchanger such as where heatedheat-exchange liquid can be present in thermally-conductive fins oracross a large thermally-conductive surface area component and a gassuch as air can be blown across the fins or large surface area to heatthe gas or air which can be useful, for example, as cabin air.

In a final example, the heated heat-exchange liquid can be delivered toan air conditioning system such as an ammonia-based air conditioningunit or system where the already-generated heat waste can be used as aheat source. The heated heat-exchange fluid such as heated water and/orglycol also can be used as a source of heat in a CHP system.

In certain designs and configurations, for example, where an exhaustconduit from an afterburner terminates within a thermally-shielded zoneor a thermally-regulated zone, the heat from the heated afterburnercombustion products also can be used to assist in heating the vaporizer,its associated fluids, and other components and fluid streams within thethermally-shielded or thermally-regulated zone. In these configurations,heated temperature-regulating fluids and heated afterburner combustionproducts can be exhausted through the one or more exhaust fluid outletsof a thermally-shielded zone or can be preferentially transferredthrough one or more faces or surfaces of a fuel cell unit and/or athermally-regulated zone.

A fuel cell system of the present teachings can be configured to exploitthe exhaust streams from the fuel cell units. For example, the exhauststreams such as heated afterburner combustion product streams fromadjacent fuel cell units can be directed towards each other and/or intoa channel present between the fuel cell units. Components and fluidstreams of the fuel cell system requiring heat can be placed orpositioned in the channel to take advantage of the heat from the opposedexhaust streams. If more than two fuel cell units are present in thefuel cell system, the additional fuel cell units can be placed orpositioned appropriately to combine their exhaust streams with theothers, if desired.

In these designs and configurations, the fuel cell units can be within athermally-shielded zone or a thermally-regulated zone, but notnecessarily. A fuel cell unit of the present teachings can define athermally-shielded zone, for example, where a liquid heat-exchange plateor a liquid heat-exchange jacket encompasses a substantial portion of afuel cell unit such as its exterior faces or surfaces and the inlet andthe outlet of the liquid heat-exchange plate or the liquid heat-exchangejacket function as the temperature-regulating fluid inlet and exhaustfluid outlet, respectively, of the thermally-shielded zone. A fuel cellunit of the present teachings can define a thermally-regulated zone, forexample, where a liquid heat-exchange plate or a liquid heat-exchangejacket encompasses a substantial portion of a fuel cell unit such as itsexterior faces or surfaces. A liquid heat-exchange jacket can be aretaining structure for a fuel cell unit where the thermal insulationaround a reformer, a fuel cell stack and an afterburner can bemaintained in place by the liquid heat-exchange jacket. A liquidheat-exchange plate or a liquid heat-exchange jacket can be in thermalcontact to varying degrees with one or more components of a fuel cellunit depending on the level of thermal control desired for a particularapplication.

A fuel cell unit of the present teachings can be designed and configuredto preferentially transfer heat from one or more faces and/or one ormore surfaces of the fuel cell unit. For example, where thermalinsulation is present around or substantially around a fuel cell unit(e.g., creating a thermal zone, which can be a thermally-shielded zone),a reduced level of thermal insulation can be in contact with, adjacentto, and/or in thermal communication with a face or a surface of the fuelcell unit thereby to increase heat transfer through or from that face orthat surface. In the design and configuration of a fuel cell system andan array of fuel cell units, a reduced level of thermal insulation canbe on, adjacent to and/or a thermal communication with the appropriatefaces or surfaces of the fuel cell units to achieve efficient andeffective heat transfer among the array of units. In certain cases, afuel cell unit can have one, two, three, four, five, six or more facesor surfaces, depending on the shape and/or design of fuel cell unit,which faces, segments thereof, or surfaces can preferentially transferheat in this way.

Indeed the design of the fuel cell units and systems of the presentteachings permits the exploitation of many of the thermal managementfeatures described herein, in various combinations, which can reduce thefootprint or package of the overall system. For example, a reduced levelof thermal insulation in contact with, adjacent to, and/or in thermalcommunication with at least one face or one surface of a fuel cell unit(e.g., of a fuel cell stack and/or an afterburner) can be associatedwith, for example, be in thermal communication with, a liquidheat-exchange plate or a liquid heat-exchange jacket thereby to transferpreferentially heat from the at least one face or one surface of thefuel cell unit to a heat-exchange liquid. Moreover, in addition toradiant heat from components of the fuel cell unit, heated exhauststreams, for example, from the afterburner, can be directed over,adjacent to and/or in (thermal) contact with a liquid heat-exchangeplate or heat-exchange jacket to provide two sources of heat for theheat-exchange liquid. Such an arrangement or configuration can reduce orminimize space requirements while increasing or maximizing heat transferand management.

The fuel cell systems described herein also can be operated as CHPsystems where a fuel cell unit and a heater unit are included in the CHPsystem. A heater unit can be envisioned as a catalytic burner that canassist in maintaining a consistent heat and power output. That is,similar to a fuel cell unit, a heater unit can convert gaseousreformable fuels into heat but without the production of electricity.The use of a heater in conjunction with a fuel cell can separate theheat output from the electrical output of the CHP system. The fuel cellunit and the heater unit can be operated independently via a userinterface to produce heat output only at a desired output level, anelectrical power with no additional heat output, or an electrical outputwith additional heat output at a desired output level. Thus, a moreconsistent heat and power output can be realized with a CHP system asthe various components of the system can be operated and adjusted asneeded to maintain the desired balance.

Although the present teachings focus on and describe fuel cell systemsand CHP systems that can be designed and constructed as a single, fixedstructure, the present teachings also encompass fuel cell systems andCHP systems that can be modular in design. That is, the fuel cell systemcan include individual fuel cell units and/or heater units that can beadded or removed from a system for design flexibility and adaptation ofthe system for a particular application, for example, to increase ordecrease power output. For example, a fuel cell unit and/or heater unitcan be connected to or disconnected from preexisting, supportingstructure include can include one or more common conduits such as acommon (reformable) fuel source conduit and a common liquidheat-exchange conduit, where such common conduits can have multipleports or interfaces for quick connection and disconnection of the fuelcell unit(s) and/or the heater unit(s). The design of the systemsdescribed herein also can permit the logical control of the flow pathsof fluids throughout the system including individual fuel cell units, ifappropriate. That is, the fluid circuit in individual fuel cell unitsand/or heater units as well as in fuel cell systems and CHP systems canbe customized for a particular application or situation such as thestart-up or shut-down of a single fuel cell unit among an array of fuelcell units.

Throughout the application, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including, or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components, or the element or component can beselected from a group consisting of two or more of the recited elementsor components.

Further, it should be understood that elements and/or features of acomposition, an apparatus, or a method described herein can be combinedin a variety of ways without departing from the spirit and scope of thepresent teachings, whether explicit or implicit herein. For example,where reference is made to a particular structure, that structure can beused in various embodiments of apparatus of the present teachings and/orin methods of the present teachings, unless otherwise understood fromthe context. In other words, within this application, embodiments havebeen described and depicted in a way that enables a clear and conciseapplication to be written and drawn, but it is intended and will beappreciated that embodiments may be variously combined or separatedwithout parting from the present teachings and invention(s). Forexample, it will be appreciated that all features described and depictedherein can be applicable to all aspects of the invention(s) describedand depicted herein.

It should be understood that the expression “at least one of” includesindividually each of the recited objects after the expression and thevarious combinations of two or more of the recited objects unlessotherwise understood from the context and use. The expression “and/or”in connection with three or more recited objects should be understood tohave the same meaning unless otherwise understood from the context. Forexample, “in contact with, adjacent to, and/or in thermal communicationwith” can mean “in contact with” or “adjacent to” or “in thermalcommunication with” or “in contact with and in thermal communicationwith” or “adjacent to and in thermal communication with” or “in contactwith and adjacent to,” although the latter phrase in the latterexpression may be considered redundant.

The use of the term “include,” “includes,” “including,” “have,” “has,”“having,” “contain,” “contains,” or “containing,” including grammaticalequivalents thereof, should be understood generally as open-ended andnon-limiting, for example, not excluding additional unrecited elementsor steps, unless otherwise specifically stated or understood from thecontext.

The use of the singular herein, for example, “a,” “an,” and “the,”includes the plural (and vice versa) unless specifically statedotherwise.

Where the use of the term “about” is before a quantitative value, thepresent teachings also include the specific quantitative value itself,unless specifically stated otherwise. As used herein, the term “about”refers to a ±10% variation from the nominal value unless otherwiseindicated or inferred.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

At various places in the present specification, values are disclosed ingroups or in ranges. It is specifically intended that the descriptioninclude each and every individual subcombination of the members of suchgroups and ranges and any combination of the various endpoints of suchgroups or ranges. For example, an integer in the range of 0 to 40 isspecifically intended to individually disclose 0, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40, and aninteger in the range of 1 to 20 is specifically intended to individuallydisclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, and 20.

The use of any and all examples, or exemplary language herein, forexample, “such as,” “including,” or “for example,” is intended merely toillustrate better the present teachings and does not pose a limitationon the scope of the invention unless claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the present teachings.

Terms and expressions indicating spatial orientation or altitude such as“upper,” “lower,” “top,” “bottom,” horizontal,” “vertical,” and thelike, unless their contextual usage indicates otherwise, are to beunderstood herein as having no structural, functional or operationalsignificance and as merely reflecting the arbitrarily chosen orientationof the various views of apparatus, devices, components, and features ofthe present teachings that may be illustrated in certain of theaccompanying figures.

As used herein, “liquid reformable fuel” refers to and includesreformable carbon- and hydrogen-containing fuels that are a liquid atstandard temperature and pressure (STP) conditions, for example,methanol, ethanol, naphtha, distillate, gasoline, kerosene, jet fuel,diesel, biodiesel, and the like, that when subjected to reformingundergo conversion to hydrogen-rich reformates. The expression “liquidreformable fuel” shall be further understood to include such fuelswhether they are in the liquid state or in the gaseous state, i.e., avapor.

As used herein, “gaseous reformable fuel” refers to and includesreformable carbon- and hydrogen-containing fuels that are a gas at STPconditions, for example, methane, ethane, propane, butane, isobutane,ethylene, propylene, butylene, isobutylene, dimethyl ether, theirmixtures, such as natural gas and liquefied natural gas (LNG), which aremainly methane, and petroleum gas and liquefied petroleum gas (LPG),which are mainly propane or butane but include all mixtures made upprimarily of propane and butane, and the like, that when subjected toreforming undergo conversion to hydrogen-rich reformates. A gaseousreformable fuel also includes ammonia, which like other gaseousreformable fuels, can be stored as a liquid.

As used herein, a “reformable fuel” refers to a liquid reformable fueland/or a gaseous reformable fuel.

As used herein, a “fuel cell stack” refers to the component of a fuelcell unit or fuel cell system where the electrochemical reaction takesplace to convert hydrogen or electrochemically-oxidizable species toelectricity. The fuel cell stack includes an anode, a cathode, and anelectrolyte, often formed in layers. In operation, hydrogen and anyother electrochemically oxidizable component(s) of a reformate enteringa fuel cell stack, for example, from a reformer and/or a fluid mixingdevice of the present teachings, combine with oxygen anions within ananode layer of the fuel cell stack to produce water and/or carbondioxide and electrons. The electrons generated within the anode layermigrate through the external load and back to the cathode layer whereoxygen combines with the electrons to provide oxygen anions whichselectively pass through the electrolyte layer and the anode layer.

As used herein, a “fuel cell unit” generally refers to a reformer inoperable fluid communication with a fuel cell stack, a fuel cell stack,and an afterburner in operable fluid communication with exhaust from thefuel cell stack. A fuel cell unit can include a vaporizer, where anoutlet of the vaporizer is in operable fluid communication with an inletof the reformer and/or the fuel cell stack. A fuel cell unit can includevarious valve assemblies, sensor assemblies, conduits, and othercomponents associated with such a unit. A “fuel cell system” generallyrefers to a fuel cell unit and the balance of plant. A fuel cell systemoften includes a plurality of fuel cell units. A plurality of fuel cellunits can share the balance of plant. However, it should be understoodthat a “fuel cell unit” and a “fuel cell system” can be usedinterchangeably herein unless the context dictates otherwise. Moreover,known and conventional fuel cells come in a variety of types andconfigurations including phosphoric acid fuel cells (PAFCs), alkalinefuel cells (AFCs), polymer electrolyte membrane (or proton exchangemembrane) fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

As used herein, a “combined heat and power system” or “CHP system”generally refers to a system that generates electricity and useableheat. A CHP system generates electricity and in doing so, can produceheat that can be captured and used in a variety of ways rather than bediscarded as waste heat. Certain types of fuel cell systems can be CHPsystems, depending on whether the reforming, electrochemical, and otherchemical reactions generate heat, i.e., are exothermic. In such systems,the thermal output typically depends on the electrical output of thefuel cell unit(s). A CHP system can include one or more fuel cell units.A CHP system can include one or more fuel cell units integrated with oneor more heater units, and the balance of plant. In such systems whereone or more heater units are present, the thermal output can beindependent of the electrical output. Accordingly, such a CHP system canprovide, at desired levels, a thermal output only, an electrical outputonly, or both thermal and electrical outputs.

As used herein, a “thermally-shielded zone” refers to a volume that canbe thermally controlled independent of the ambient environment and/orother adjacent volume(s) outside of the thermally-shielded zone. Athermally-shielded zone can include a “thermally-isolated zone;”however, a thermally-shielded zone typically has one or moretemperature-regulating fluid inlets and one or more exhaust fluidoutlets, where the inlet(s) and the outlet(s) provide fluidcommunication such as operable fluid communication between the interiorand the exterior of the thermal zone, so that a thermally-shielded zoneis not completely isolated thermally from the ambient environment. Athermally-shielded zone has no or substantially no heat transfer occurthrough and/or from a face or a surface of the structure defining thethermally-shielded zone other than through the one or moretemperature-regulating fluid inlets, one or more exhaust fluid outlets,and any other conduits traversing the thermally-shielded zone thatdeliver fluids to and from a fuel cell unit and associated components,for example, to permit operation of the fuel cell unit such as an anodereactants conduit, a cathode air conduit, and an exhaust conduit.

A thermally-shielded zone can be created with a box or a box-likestructure over a fuel cell unit, where the box or the box-like structurecan have one or more temperature-regulating fluid inlets and one or moreexhaust fluid outlets. In such a case, the barriers or walls of the boxor the box-like structure can define the thermally-shielded zone. Invarious embodiments, a thermally-shielded zone can be created in variousshapes and/or configurations using thermally non-conductive materials,for example, thermal insulation materials such as sheets of solidthermal insulation material, to form and define a volume that isthermally shielded from the ambient environment but fortemperature-regulating fluid inlet(s) and exhaust fluid outlet(s). Insome embodiments, a thermally-shielded zone can be defined by the fuelcell unit itself, for example, where a liquid heat-exchange plate or aliquid heat-exchange jacket is in thermal communication with the fuelcell unit. In these cases, the liquid heat-exchange plate or the liquidheat-exchange jacket typically will be in thermal communication with theentire or substantially the entire fuel cell unit, for example,surrounding or encompassing the fuel cell unit, at least on its exposedvertical surfaces.

As used herein, a “thermally-regulated zone” refers to a volume that canbe thermally controlled independent of the ambient environment and/orother adjacent volume(s) outside of the thermally-regulated zone but forwhich heat transfer can occur through and/or from a face, a segmentthereof, or a surface of the thermally-regulated zone. Athermally-regulated zone can have one or more temperature-regulatingfluid inlets and one or more exhaust fluid outlets. In variousembodiments, a thermally-regulated zone can permit preferential heattransfer to occur from the thermally-regulated zone, for example, byhaving different amounts or levels of thermal insulation present thatdefine the thermally-regulated zone. For example, certain portions orareas of one or more faces or surfaces defining a thermally-regulatedzone can include a reduced level of thermal insulation to permitpreferential heat transfer as described herein.

Preferential heat transfer can be facilitated by a source of positivegas pressure in operable fluid communication with one or moretemperature-regulating fluid inlets of a thermally-regulated zone. Insuch cases, the source of positive gas pressure such as a fan, a bloweror a compressor can move air within the thermally-regulated zone to anexhaust fluid outlet and/or an area of reduced thermal insulation. Athermally-regulated zone can be created similar to the creation of athermally-shielded zone but with less stringent requirements to preventheat transfer through and/or from a surface or a face or a segment of aface of the thermally-regulated zone. That is, preferential heattransfer from a face, or segment thereof, or a surface of a fuel cellunit and the adjacent face, segment or surface of the structure (e.g.,solid thermal insulation) defining the thermally-regulated zonetypically is the desired result with a thermally-regulated zone.

As used herein, “in operable fluid communication with” refers to fluidcommunication between or among various components and/or structure whenthe components and/or structure are in an operative or active state orposition; however, fluid communication can be interrupted when thecomponents and/or structure are in an inoperative or inactive state orposition. Operable fluid communication can be controlled by a valveassembly positioned between or among components and/or structure. Forexample, if A is in operable fluid communication with B via a valveassembly, then fluid can flow or be delivered from A to B when the valveassembly is “open” thereby permitting fluid communication between A andB. However, fluid communication between A and B can be interrupted orceased when the valve assembly is “closed.” In other words, the valveassembly is operable to provide fluid communication between A and B. Itshould be understood that fluid communication can include variousdegrees and rates of fluid flow and related characteristics. Forexample, a fully-opened valve assembly can provide fluid communicationbetween or among components and/or structure as can the valve assemblywhen it is partially-closed; however, the fluid flow characteristicssuch as flow rate can be affected by the different positions of thevalve assembly. As used herein, “in operable fluid communication with”and “in fluid communication with” can be used interchangeably unless thecontext dictates otherwise.

As used herein, “in thermal communication with” refers to thermalcommunication between or among various components and/or structure suchthat heat transfer can occur between or among the components and/orstructure. Although components and structure typically in thermalcommunication remain in thermal communication, where the thermalcommunication can be interrupted, for example, ceasing the flow ofheated fluids to components and/or structure or placing an insulationbarrier or structure between or among components and/or structure, “inoperable thermal communication with” can be a more appropriateexpression similar to the expression and meaning of “in operable fluidcommunication with.” However, as used herein, “in thermal communicationwith” and “in operable thermal communication with” can be usedinterchangeably unless the context dictates otherwise.

As used herein, to “control the flow,” “control the delivery,” “adjustthe flow,” and “adjust the delivery” of a fluid, including grammaticalequivalents and equivalent expressions and language, can be to increasethe flow or delivery of fluid, to decrease the flow or delivery offluid, to maintain a substantially constant flow or delivery of fluid,and/or to interrupt or cease the flow or delivery of fluid.

Similarly, to “control the pressure” and “adjust the pressure,”including grammatical equivalents and equivalent expressions andlanguage, can be to increase the pressure, to decrease the pressure, tomaintain a substantially constant pressure, and/or to interrupt or ceasethe pressure. It should be understood that in many circumstances, to“control the flow” and “adjust the flow” can be to “control thepressure” and “adjust the pressure,” and vice versa. In addition,“controlling,” “adjusting,” and “manipulating” a component of a fuelcell unit, a heater unit, a fuel cell system, or a CHP system (includinggrammatical equivalents and equivalent expressions and language), forexample, a valve assembly or a source of positive gaseous pressure, caneffect the same changes and/or steady-state operation as describedabove.

As used herein, a “valve assembly” refers to a structure or structurestogether that can monitor and/or control fluid communication and fluidflow characteristics between or among components and/or structure, forexample, the delivery of a reformable fuel to a reformer or the flow ofheat exchange liquid through a liquid heat exchange plate or a liquidheat-exchange jacket. A valve assembly can be a single valve or includea plurality of valves and related structure, where certain structurescan be in series. A valve assembly can be or include a pressure meteringassembly. For example, a valve assembly can be or include a meteringvalve thereby permitting digital control of the flow and delivery offluids. A valve assembly can be or include valves in a piccoloarrangement, for example, a series of orifices, each associated with aproportional valve. A valve assembly can include a proportional valvesuch as a proportional solenoid valve; or a series of proportionalvalves such as a series of proportional solenoid valves. A valveassembly can include an on/off valve such as a solenoid valve; or aseries of on/off valves, for example, a series of on/off solenoidvalves. A valve assembly can include a three-way valve; a series ofthree-way valves; a check valve; a series of check valves; an orifice; aseries of orifices; and combinations thereof and of the other valves andvalve assemblies described herein, where certain of the valves and valveassemblies can be in series. Where structures or components areindicated as being in series, the components can be either in a parallelseries or in a sequential series (e.g., collinear).

As used herein, a “sensor assembly” refers to any suitable sensor orsensing device or combination of sensor or sensing devices for theoperating parameter(s) being monitored, measured and/or determined. Forexample, fuel flow rates can be monitored with any suitable flow meter,pressures can be monitored with any suitable pressure-sensing orpressure-regulating device, and temperatures can be monitored with anysuitable temperature sensor. Accordingly, examples of sensor devicesinclude flow meters, pressure meters, thermocouples, thermistors, andresistance temperature detectors. A sensor or sensing device can includea balance, a weighing scale such as a spring scale, or other device formonitoring, measuring, and/or determining the weight of an object. Thesensor assemblies optionally can include a transducer in communicationwith the controller.

As used herein, a “source of positive gaseous pressure” or a “source ofpositive gas pressure” refers to device or apparatus that can produce apositive gaseous or gas pressure or cause gas movement. A source ofpositive gas pressure can be a positive displacement blower, pump orcompressor, or a dynamic blower, pump or compressor. Examples of sourcesof positive gaseous or gas pressure include a fan, a plurality or seriesof fans, a rotary pump or compressor, such as a rotary vane pump orcompressor, a plurality or a series of rotary pumps or compressors, areciprocating pump or compressor such as a diaphragm pump or compressor,or a plurality or a series of diaphragm pumps or compressors, a blower,for example, a centrifugal blower or compressor, a plurality or seriesof blowers, a plurality or series of centrifugal blowers or compressors,an air pump, a container of compressed gas such as a tank of air or aninert gas, and combinations thereof. A “positive gaseous pressure” or a“positive gas pressure” can be realized from any of these sources ofpositive gas pressure and others known to those skilled in the art.

In operation, a pump, such as a liquid pump or a fuel pump, cancirculate liquids and/or reformable fuels through the fuel cell or CHPsystem. For example, a pump can flow reformable fuels to a vaporizerand/or a reformer of a fuel cell unit. A pump can be used to circulateliquid, for example, water and/or a glycol, through a liquidheat-exchange plate or a liquid heat-exchange jacket. Examples of a pumpsuch as a liquid or fuel pump include a metering pump, a rotary pump, animpeller pump, a diaphragm pump, a peristaltic pump, a positivedisplacement pump, a gear pump, a piezoelectric pump, an electrokineticpump, an electroosmotic pump, and a capillary pump. The pump can controlthe flow rate of liquids and/or reformable fuels through a fuel cell orCHP system.

The exemplary fuel cell systems and CHP systems depicted in the figuresinclude various conduits, for example, a cathode air conduit, an anodereactants conduit, an afterburner exhaust conduit, and the like. A fuelcell or CHP system of the present teachings can include a plurality ofconduits, for example, two or more conduits, positioned to provideoperable fluid communication between or among components of the fuelcell or CHP system. A plurality of conduits also can couple a fuel cellunit or fuel cell or CHP system, for example, to components common tothe fuel cell or CHP system such as a vaporizer and/or reformable fuelsource. That is, the components of the fuel cell or CHP systems andmethods of the present teachings including peripheral components anddevices can include conduits connecting or linking the components, forexample, a vaporizer, a (hydrocarbon fuel) reformer, and relatedequipment such as valve assemblies, pumps, and sensor assemblies. Eachof these components and others can include one or more of an inlet, anoutlet, and a port to permit fluid communication, for example, operablefluid communication, to be established between or among the components.It also should be understood that the conduits can include othercomponents and devices associated therewith, for example, valveassemblies, pumps, sources of positive gaseous pressure, and sensorassemblies.

The conduits or conduit system can have many specific designs,configurations, arrangements, and connections depending on many factors,for example, the particular application, the reformable fuel, and thefootprint size of the overall fuel cell or CHP system. Thus, the conduitsystems described and/or shown herein are merely for illustrativepurposes and are not meant to limit the present teachings in any way.Moreover, where two or more conduits may be described as connected to,coupled to, or otherwise joining a component or components, for example,a valve assembly and a source of reformable fuel, a single conduit alsocan be envisioned as achieving the same design and/or purpose, where thecomponent such as a valve assembly can be described as being “in-linewith,” “situated within,” or “associated with” a single conduit. Inaddition, “coupled to,” “connected to” or otherwise joining two or morecomponents or structure can mean that the one component or structure isdirectly or indirectly coupled, connected or joined to another componentor structure.

A conduit can be a duct, for example, a channel, tube or passageway forconveying a fluid. For example, a temperature-regulating fluid conduitcan be used to carry or deliver a temperature-regulating fluid, forexample, ambient air external to a fuel cell unit or system, through atemperature-regulating fluid inlet to a fuel cell unit within athermally-shielded zone or a thermally-regulated zone. As anotherexample, an exhaust conduit can be used to carry or deliver exhaustfluids away from a fuel cell unit, for example, from an afterburner tothe exterior of the fuel cell unit, either within a thermally-shieldedzone or a thermally-regulated zone, or outside or exterior to suchzones. A conduit can be a manifold, for example, a chamber, pipe or ductwith a number of inlets or outlets used to collect or distribute afluid. As used herein, a “common conduit” generally refers to amulti-ported conduit for fluid delivery to and/or from specificlocations.

A fuel cell unit, a fuel cell system, a heater unit, and a CHP system ofthe present teachings can include a control system for automating theoperations of the individual units, components thereof, and/or of theoverall system. A control system can include control components, forexample, control electronics, actuators, valve assemblies, sensorassemblies, and other structure and devices to monitor, control and/oradjust the operation of an individual fuel cell unit or heater unit; oneor more components thereof such as a vaporizer, a reformer, a fuel cellstack and an afterburner; a fuel cell system or a CHP system; and one ormore components thereof such as the balance of plant, for example, asource of positive gas pressure.

A control system can include a controller, which can be in communicationwith the various control components and components of each fuel cellunit and/or heater unit. The control system and/or controller canmonitor and logically control the flow path of fluids (e.g., liquid andgaseous reactants such as reformable fuel, an oxygen-containing gas andsteam; air such as temperature-regulating air, radiated heated air, andcathode air; exhaust streams; and heat-exchange liquid) throughindividual components of a fuel cell unit or a heater unit, throughindividual fuel cell units or heater units, and through a fuel cellsystem or a CHP system. In other words, a custom fluid circuit can beachieved in a fuel cell system or a CHP system using a control system.

For example, in various embodiments, a fuel cell unit can be coupled toa common fuel source conduit and/or a common liquid heat-exchangeconduit. Such coupling can occur while the fuel cell system is notoperating. However, such coupling can occur when the fuel cell system isoperating, for example, to swap out an inefficiently functioning fuelcell unit. In the latter case, the coupling can occur to the commonconduits without initiating the delivery of fuel and/or heat-exchangeliquid to the newly-coupled fuel cell unit until desired.

In addition, because the newly-coupled fuel cell unit is of ambienttemperature, the start-up mode for that fuel cell unit can be operatedindependent of the operation of the other fuel cell units that areoperating in steady-state mode, for example, to avoid dissipating heatfrom the operating fuel cell units. Accordingly, the newly-coupled fuelcell unit can be run in start-up mode, where the control systemindependently controls the valve assemblies and other components for thedelivery of fuel, air, other fluids, and heat to that fuel cell unituntil operating in a steady-state mode, when its operations can becombined with those of the already-operating fuel cell units, ifdesired. In the same fashion, an individual fuel cell unit of a fuelcell system can undergo a shut-down mode independent of the otheroperating fuel cell units thereby to permit the fuel cell system tocontinue to generate electricity while replacing the particular fuelcell unit.

In certain methods of the present teachings, the heated fluid streamsgenerated by one or more operating fuel cell units such as heatedheat-exchange liquid in thermal communication with such units can bediverted to a “cold” fuel cell unit such as a newly-coupled fuel cellunit in a fuel cell or CHP system to facilitate start-up of the “cold”fuel cell unit. That is, the heated fluid streams from the operatingfuel cell units can be directed to or partially diverted to a “coldpackage” to assist in heating the various components of a fuel cellunit, for example, one or more of the reformer, the fuel cell stack, andthe afterburner, while in start-up mode. Likewise, heated heat-exchangeliquid associated with operating fuel cell unit(s) can be directed to orpartially diverted to a liquid heat-exchange plate or a liquidheat-exchange jacket in thermal communication with one or morecomponents of the cold fuel cell unit to provide heat to the outside ofone or more components of the fuel cell unit. The use of heat from theoperating units, whether heated gaseous streams and/or heatedheat-exchange liquid can reduce start-up times for the cold fuel cellunit, for example, assisting in initiating catalytic activity within oneor more components of the fuel cell unit.

As can be inferred from the foregoing, a fuel cell unit can include fuelcell unit control components that can be configured or adapted tocommunicate and control operations within the fuel cell unit. A fuelcell or CHP system can include fuel cell system control components orCHP system control components, respectively, that can be configured oradapted to communicate among the individual fuel cell units and heaterunits, if present, and control the operations of the fuel cell or CHPsystem. The fuel cell system control components and the CHP systemcontrol components can be in communication with the individual fuel cellunits and heater units, if present.

The control system can include a one or more sensors or sensorassemblies in communication with a controller. In response to inputsignals from the sensor assemblies, user commands from a user-inputdevice and/or programmed subroutines and command sequences, a controllercan manage independently the operations of one or more fuel cell unitsand/or heater units, or of the overall fuel cell or CHP system. Thecontroller can be software operating on a processor. However, it iswithin the scope of the present teachings to employ a controller that isimplemented with one or more digital or analog circuits, or combinationsthereof.

The sensor assemblies can, but do not necessarily, include a transducerin communication with the controller. The communication pathways willordinarily be wired electrical signals but any other suitable form ofcommunication pathway can also be employed. That is, the sensorassemblies, control signal-receiving devices, and communication pathwaysherein can be of any suitable construction. A wireless communicationpathway can be used, such as a Bluetooth connection. The wirelesscommunication pathway(s) can be part of a wireless network that useswireless data connections for connecting network nodes. A combination ofwired and wireless communication pathways can be used.

A fuel cell unit typically includes power conditioning components thatcan be configured or adapted to convert the electrical output of a fuelcell stack into a regulated electrical output of the fuel cell unit.Power conditioning components, which can be referred to as powerhandling components or power management components, can include currentcollection plates and/or bus bars that can carry the electrical currentaway from the fuel cell stack and deliver it external to the fuel cellunit. Power conditioning components typically are located close to thefuel cell stack where the electricity is generated. As such, powerconditioning components can be exposed to the high operatingtemperatures of the fuel cell stack and the fuel cell unit.Nevertheless, heat transfer away from such components such as with theuse of a liquid heat-exchange plate or a liquid heat-exchange jacketadjacent to or around a fuel cell unit and/or at least adjacent to thepower conditioning components can reduce the electrically resistivelosses.

In contrast, the electronics of a fuel cell system associated with acontrol system and a controller sensor assemblies and/or valveassemblies for monitoring and operating the various components of a fuelcell unit, fuel cell system and/or CHP system typically are heatsensitive. Accordingly, such electronics typically are inthermally-protected locations or environments, for example, outside of athermally-shielded zone including a fuel cell unit and/or adjacent to orencompassed by sufficient thermal insulation such as solid and/or liquidthermal insulation.

Accordingly, the present teachings provide a fuel cell system that caninclude a fuel cell unit. The fuel cell unit can include a reformer; afuel cell stack in operable fluid communication with the reformer; andan afterburner in operable fluid communication with the fuel cell stack.The fuel cell unit can be within a thermally-shielded zone. Athermally-shielded zone can include a thermal insulation such as a solidthermal insulation, a fluid thermal insulation, or combinations thereof.A thermally-shielded zone can be defined by a thermal insulation such asa solid thermal insulation, a fluid thermal insulation, or combinationsthereof. Each thermally-shielded zone can include atemperature-regulating fluid inlet and one or more exhaust fluidoutlets. A source of positive gaseous pressure can be in operable fluidcommunication with the temperature-regulating fluid inlet and one ormore of the reformer, the fuel cell stack and the afterburner.

A fuel cell system can include a first fuel cell unit and a second fuelcell unit. The first fuel cell unit and the second fuel cell unitindependently can be a fuel cell unit of present teachings. A fuel cellsystem can include more than two fuel cell units, for example, three,four, five, six or more fuel cell units.

A fuel cell unit, or independently each of the first fuel cell unit,second fuel cell unit, and any higher order fuel cell unit can include acathode air conduit in operable fluid communication with a cathode ofthe fuel cell stack and configured to deliver cathode air (anoxygen-containing gas) to the cathode. A fuel cell unit, orindependently each of the first fuel cell unit, second fuel cell unit,and any higher order fuel cell unit can include an anode reactantsconduit in operable fluid communication with an anode of the fuel cellstack and configured to delivery one or more of anode air, an oxidantsuch as steam, and a (reformed) reformable fuel to the anode. In certainembodiments, a reformable fuel can be delivered directly to an anode ofa fuel cell stack prior to being reformed. In such cases, a reformingcatalyst is incorporated into the anode (fuel) electrodes of the fuelcell stack such that “on-cell” reforming can occur. A fuel cell unit, orindependently each of the first fuel cell unit, second fuel cell unit,and any higher order fuel cell unit can include an exhaust conduit inthermal and operable fluid communication with the afterburner andconfigured to exhaust heated combustions products from the afterburner.

The exhaust conduit includes an upstream end and a downstream end. Thedownstream end of the exhaust conduit can terminate within thethermally-shielded zone. In such embodiments and other embodiments ofthe present teachings, the fuel cell unit, or independently each of thefirst fuel cell unit, the second fuel cell unit and any higher orderfuel cell units, can include a vaporizer in thermal communication withheated afterburner combustion products and in operable fluidcommunication with the reformer.

In various embodiments, the downstream end of the exhaust conduit canterminate outside of the thermally-shielded zone. In these and relatedembodiments, where the fuel cell system includes at least a first fuelcell unit and a second fuel cell unit, the downstream end of the exhaustconduit of first fuel cell unit can be directed towards the downstreamend of the exhaust conduit of the second fuel cell unit whereby theexhaust streams from each fuel cell unit are configured to combine. Theheated afterburner combustion products from the exhaust conduits can bedirected to heat other components of the fuel cell system outside of thethermally-shielded zones, for example, a vaporizer, reformable fuel,cathode air, and anode air. The heated afterburner combustion productsfrom the exhaust conduits can be directed to and/or be in thermalcommunication with a heat-exchange liquid such as a heat-exchange liquidin a liquid heat-exchange plate or a liquid heat-exchange jacket.

In some embodiments, a fuel cell system can include at least a firstfuel cell unit and a second fuel cell unit, where each fuel cell unitcan include a reformer; a fuel cell stack in operable fluidcommunication with the reformer; and an afterburner in operable fluidcommunication with the fuel cell stack.

Thermal insulation such as solid thermal insulation and/or fluid thermalinsulation can be distributed about the fuel cell unit such that areduced level of thermal insulation can be in contact with, adjacent to,and/or in thermal communication with at least one face, a segmentthereof, or one surface of the first fuel cell unit, for example,adjacent to at least the fuel cell stack of the first fuel cell unitand/or the fuel cell stack of the second fuel cell unit, thereby toincrease heat transfer through and/or from the at least one face, thesegment thereof, or one surface associated with the reduced level ofthermal insulation. A reduced level of thermal insulation can be presentin contact with, adjacent to, and/or in thermal communication with oneor more faces or surfaces of one or more of a reformer, a fuel cellstack, an afterburner, and a vaporizer, if present.

In certain embodiments, at least one face or one surface of the firstfuel cell unit associated with a reduced level of thermal insulation canbe opposed to at least one face or one surface of the second fuel cellunit associated with a reduced level of thermal insulation.

In particular embodiments, where the fuel cell system further includes athird fuel cell unit, and the first fuel cell unit, the second fuel cellunit and the third fuel cell unit are in series, at least one face orone surface of the first fuel cell unit associated with a reduced levelof thermal insulation can be opposed to at least one face or one surfaceof the second fuel cell unit associated with a reduced level of thermalinsulation and a second face or surface of the second fuel cell unitassociated with a reduced level of thermal insulation can be opposed toat least one face or one surface of the third fuel cell unit associatedwith a reduced level of thermal insulation.

In such and other embodiments of the present teachings, the second fuelcell unit can include a third face or surface associated with a reducedlevel of thermal insulation, i.e., where a reduced level of thermalinsulation can be in contact with, adjacent to, and/or in thermalcommunication with a third face or surface of the second fuel cell unit.

In some embodiments including the configurations described above, thefirst, second and third fuel cell units can define a first set of fuelcell units and the fuel cell system further can include a second set offuel cell units. The second set of fuel cell units can be substantiallysimilar to the first set of fuel cell units and can be positioned suchthat the third face of the second fuel cell unit of the first set offuel cell units is opposed to the third face of the second fuel cellunit of the second set of fuel cell units.

In designs and embodiments including a reduced level of thermalinsulation on or adjacent to one or more faces, segments thereof, orsurfaces of a fuel cell unit, the fuel cell unit(s) can be within athermally-regulated zone. The thermally-regulated zone can include atemperature-regulating fluid inlet and one or more exhaust fluidoutlets. The thermally-regulated zone can include a source of positivegas pressure in operable fluid communication with thetemperature-regulating fluid inlet(s) and one or more of the reformer,the fuel cell stack, and the afterburner. The thermally-regulated zonecan include a solid thermal insulation, a fluid thermal insulation, orcombinations thereof. The thermally-regulated zone can be defined by asolid thermal insulation, a fluid thermal insulation, or combinationsthereof.

Each of the first fuel cell unit and the second fuel cell unitindependently can include a cathode air conduit in operable fluidcommunication with a cathode of the fuel cell stack and configured todeliver cathode air to the cathode. Each of the first fuel cell unit andthe second fuel cell unit independently can include an anode reactantsconduit in operable fluid communication with an anode of the fuel cellstack and configured to delivery one or more of anode air, an oxidant,and reformable fuel to the anode. Each of the first fuel cell unit andthe second fuel cell unit independently can include an exhaust conduitin thermal and operable fluid communication with the afterburner andconfigured to exhaust heated afterburner combustion products from theafterburner.

In various embodiments, the exhaust conduit includes an upstream end anda downstream end, where the downstream end of the exhaust conduitterminates within the thermally-regulated zone. In some embodiments, theexhaust conduit includes an upstream end and a downstream end, where thedownstream end of the exhaust conduit terminates outside thethermally-regulated zone. In certain embodiments, the downstream end ofthe exhaust conduit of a first fuel cell unit can be directed towardsthe downstream end of the exhaust conduit of a second fuel cell unitwhereby the exhaust streams from each fuel cell unit are configured tocombine, which can be in a channel between the fuel cell units therebycreating a “heated zone.”

Each of a first fuel cell unit and a second fuel cell unit independentlycan include a vaporizer in thermal communication with the heatedafterburner combustion products and in operable fluid communication withtheir respective reformers.

In various embodiments, a fuel cell system of the present teachingsincludes at least a first fuel cell unit and a second fuel cell unit,where each fuel cell unit independently includes a reformer; a fuel cellstack in operable fluid communication with the reformer; an afterburnerin operable fluid communication with the fuel cell stack; and an exhaustconduit in thermal and operable fluid communication with theafterburner. The exhaust conduit includes an upstream end and adownstream end. The downstream end of the exhaust conduit of first fuelcell unit can be directed towards the downstream end of the exhaustconduit of the second fuel cell unit whereby the exhaust streams fromeach fuel cell unit are configured to combine.

A source of positive gaseous pressure can be located between the firstand the second fuel cell units, and in operable fluid communication withthe exhaust conduits and exhaust streams from each fuel cell unitwhereby the exhaust streams, for example, containing heated afterburnercombustion products, can be moved or directed to other components of thefuel cell system and/or exhausted from the fuel cell system. A fuel cellsystem further can include two or more sources of positive gaseouspressure in fluid communication with the exhaust conduits to controlbetter the thermal environment of the fuel cell system.

For example, the exhaust conduit of each fuel cell unit can beconfigured to exhaust heated fluid such as heated afterburner combustionproducts from the afterburner to at least one of a vaporizer, a common(reformable) fuel source conduit, a common cathode air conduit, and asource of liquid such as a liquid reformable fuel or water (forgenerating steam). At least one of the vaporizer, the common(reformable) fuel source conduit, the common cathode air conduit, andthe source of liquid can be positioned in a channel between the firstfuel cell unit and the second fuel cell unit, and the exhaust conduitscan be configured to exhaust heated fluid (combustion products) from theafterburner into the channel. The heated fluids exhausted into thechannel between the fuel cell units can create a “heated zone” wherebythe heat can be used to heat one or more of the vaporizer, the common(reformable) fuel source conduit, the common cathode air conduit, andthe source of liquid. In addition, the fuel cell units can include areduced level of thermal insulation on the face, a segment thereof, or asurface that is facing the channel to increase the heat transfer intothe channel. In certain embodiments, the common fuel source conduit or asource of liquid such as a liquid reformable fuel reservoir or otherstructure can include a heat-activated absorbent to remove contaminantssuch as sulfur from the (reformable) fuel as it passes through theheated zone or channel.

A fuel cell system further can include two or more sources of positivegaseous pressure in fluid communication with the exhaust conduits andthe channel. The two or more sources of positive gaseous pressure can beconfigured independently to control the delivery of heated fluid fromthe exhaust conduits into the channel.

In various embodiments, a fuel cell unit of the present teachings caninclude a reformer; a fuel cell stack in operable fluid communicationwith the reformer; an afterburner in operable fluid communication withthe fuel cell stack; and a vaporizer in thermal communication with theafterburner and in operable fluid communication with the reformer. Thefuel cell unit can be within a thermally-shielded zone. Thethermally-shielded zone can include a temperature-regulating fluid inletand one or more exhaust fluid outlets. A source of positive gaseouspressure can be in operable fluid communication with thetemperature-regulating fluid inlet and one or more of the vaporizer, thereformer, the fuel cell stack and the afterburner.

The fuel cell unit can include a cathode air conduit in operable fluidcommunication with a cathode of the fuel cell stack; an anode airconduit in operable fluid communication with the vaporizer; and areformable fuel conduit in operable fluid communication with thevaporizer.

The fuel cell unit can include an exhaust conduit in thermal andoperable fluid communication with the afterburner. The exhaust conduitcan be in thermal communication with the anode air conduit. The exhaustconduit can be in thermal communication with the vaporizer.

The various fuel cell systems and fuel cell units of the presentteachings can include a liquid heat-exchange plate or a liquidheat-exchange jacket in thermal communication with one or more of areformer, a fuel cell stack, and an afterburner of a fuel cell unit, ora first fuel cell unit, a second fuel cell unit, and any higher orderfuel cell units. The liquid heat-exchange jacket can encompass one ormore of the reformer, the fuel cell stack, and the afterburner of one ormore fuel cell units. A liquid heat-exchange plate or a liquidheat-exchange jacket can be in thermal communication with a face orsegment thereof or a surface of one or more fuel cell units associatedwith a reduced level of thermal insulation thereby to transfer heatpreferentially from the face, the segment thereof, or the surface to aheat-exchange liquid.

It should be understood that when reference is made herein to a face ofa fuel cell unit or other structure, a segment of the face of the fuelcell unit or other structure is intended to be included unless otherwisestated or inferred from the context. For example, a face of a fuel cellunit can include a reformer, a fuel cell stack and an afterburner, oftenin such sequential order. A segment of a face of a fuel cell unit caninclude one or more of the reformer or a portion of the reformer, thefuel cell stack or a portion of the fuel cell stack, and the afterburneror a portion of the afterburner. In addition, a segment of a fuel cellstack can include one or more segments as the word “a” is definedherein. That is, a segment of a face of a fuel cell stack can refer tothe reformer and the afterburner, where the fuel cell stack is excludedand not part of the segment.

The liquid heat-exchange plate or the liquid heat-exchange jacket caninclude an interface configured to connect the liquid heat-exchangeplate or the liquid heat-exchange jacket to a common liquidheat-exchange conduit of a fuel cell system. The interface between theliquid heat-exchange plate or the liquid heat-exchange jacket and thecommon liquid heat-exchange conduit can include a valve assembly. Thevalve assembly can include one or more of a quick-connect valve, a fixedorifice, and a proportional valve. Each of the quick-connect valve, thefixed orifice, and the proportional valve can be to provide operablefluid communication between the liquid heat-exchange plate or the liquidheat-exchange jacket and the common liquid heat-exchange conduit.

In the various fuel cell systems of the present teachings, where fuelcell unit includes a reformer, an interface can be configured to connectthe reformer to a common fuel source conduit of the fuel cell system.The interface between the reformer and the common fuel source conduitcan include a valve assembly. The valve assembly can include one or moreof a quick-connect valve, a fixed orifice, and a proportional valve.Each of the quick-connect valve, the fixed orifice, and/or theproportional valve can be configured to provide operable fluidcommunication between the reformer and the common gaseous fuel sourceconduit.

The fuel cell systems and fuel cell units of the present teachings caninclude a control system for automating the operations of the fuel cellsystem such as independently each fuel cell unit and/or componentsthereof, for example, the source(s) of positive gaseous pressure and/orthe liquid heat-exchange plate or the liquid heat-exchange jacket. Thecontrol system can include a controller in communication with one ormore sensor assemblies and/or one or more valve assemblies associatedwith the source(s) of positive gaseous pressure and/or the liquidheat-exchange plate or the liquid heat-exchange jacket, conduitsassociated therewith, and/or components of each fuel cell unit. The oneor more sensor assemblies independently can include a temperature sensorand/or a pressure sensor.

In some embodiments, the electronics of a fuel cell unit can be locatedoutside of a thermally-shielded zone or outside of a thermally-regulatedzone. In certain embodiments, the electronics of a fuel cell unit can belocated on or adjacent to a face or a surface of a fuel cell unit notassociated with a reduced level of thermal insulation (e.g., a face,segment thereof, or surface having non-reduced level of thermalinsulation). In particular embodiments, the electronics of a fuel cellunit can be located on or adjacent to the opposite face or surface ofthe downstream end of an exhaust conduit.

The present teachings also include a CHP system. A CHP system caninclude one or more fuel cell systems or units of the present teachings;and a heater unit positioned adjacent to the fuel cell unit. A CHPsystem can include a control system for automating independently theoperations of individual fuel cell units and heater units of the CHPsystem. The control system can include a controller in communicationwith one or more sensor assemblies and/or one or more valve assemblies,the one or more sensor assemblies and/or one or more valve assembliesindependently associated with fuel cell unit(s) and/or heater unit(s).

Another aspect of the present teachings relates to methods of thermallymanaging a fuel cell system, fuel cell unit(s), and/or a CHP system. Amethod of thermally managing a fuel cell system can include deliveringtemperature-regulating fluids through a temperature-regulating fluidinlet of a thermally-shielded zone; and exhausting heated exhaust fluidsthrough one or more exhaust fluid outlets of the thermally-shieldedzone. A fuel cell unit can be within a thermally-shielded zone. Theheated exhaust fluids can include heated temperature-regulating fluids.That is, the heated exhaust fluids can include temperature-regulatedfluids introduced through the temperature-regulating fluid inlet thatare heated as the fluids move through the thermally-shielded zone beforebeing exhausted.

In various embodiments, delivering temperature-regulating fluids througha temperature-regulating fluid inlet of a fuel cell unit can includedelivering independently temperature-regulating fluids through atemperature-regulating fluid inlet of a first fuel cell unit and througha temperature-regulating fluid inlet of a second fuel cell unit. In someembodiments, exhausting heated exhaust fluids through one or moreexhaust fluid outlets of the fuel cell unit can include exhaustingindependently heated exhaust fluids through one or more exhaust fluidoutlets of the first fuel cell unit and from one or more exhaust fluidoutlets of the second fuel cell unit. The first fuel cell unit can bethermally-shielded from the second fuel cell unit. The heated exhaustfluids can include heated temperature-regulating fluids.

In particular embodiments, the methods can include exhausting within athermally-shielded zone heated afterburner combustion products from anafterburner of a fuel cell unit. The heated exhausted fluids can includeheated afterburner combustion products from the afterburner of the fuelcell unit. In certain embodiments, the methods can include heating avaporizer with heated afterburner combustion products from anafterburner of a fuel cell unit. The methods can include heating withheated afterburner combustion products from an afterburner of a fuelcell unit anode air prior to delivery to a vaporizer. The methods caninclude heating with heated afterburner combustion products from theafterburner of a fuel cell unit reformable fuel prior to delivery to avaporizer. The methods can include heating with heat from theafterburner cathode air prior to delivery to a cathode of a fuel cellunit. In the latter methods the cathode air can pass through theafterburner prior to delivery to the cathode.

In various embodiments, methods of thermally managing a fuel cell systemcan include exhausting heated fluid from a first fuel cell unit towardsa second fuel cell unit; and exhausting heated fluid from the secondfuel cell unit towards the first fuel cell unit.

Such an arrangement can be useful in a staged start-up of a plurality offuel cell units of a fuel cell system. For example, where only one fuelcell unit initially is running or operated due to the power requirementsof the application but additional power is needed, the second fuel cellunit can be started. Because the (first) operating fuel cell unit isexhausting its heated fluids towards the second (non-operating) fuelcell unit, the second fuel cell unit is already heated at leastpartially to facilitate its start-up and reduce the time for the secondfuel cell unit to reach steady-state operation.

In some embodiments, exhausting heated fluid comprises exhaustingindependently heated afterburner combustion products from an afterburnerof each of a first fuel cell unit and a second fuel cell unit. In someembodiments, each of the first fuel cell unit and the second fuel cellunit independently can be within a thermally-shielded zone. Inparticular embodiments, exhausting heated fluid can include exhaustingindependently heated afterburner combustion products from an afterburnerof each of the first fuel cell unit and the second fuel cell unitoutside a thermally-shielded zone of each of the first fuel cell unitand the second fuel cell unit, respectively.

The methods can include directing exhausted heated fluid from a firstfuel cell unit and a second fuel cell unit to a channel formed by andbetween the first fuel cell unit and the second fuel cell unit. Inparticular embodiments, directing the exhausted heated fluid can includedirecting exhausted heated fluid such as heated afterburner combustionproducts to at least one of a vaporizer and a source of fluid located inthe channel. The source of fluid can be a source of water. In suchembodiments, the method can include heating the water for use in steamreforming.

A method of thermally managing a fuel cell system can include exhaustingheated fluid from a first fuel cell unit towards a second fuel cell unitto reduce the time to initiate chemical reaction or start-up in thesecond fuel cell unit in comparison to the time to initiate chemicalreaction or start-up in the second fuel cell unit without the benefit ofexhausted, heated fluid from the first fuel cell unit.

In various embodiments, methods of thermally managing a fuel cell systemcan include transferring heat preferentially from a face, a segmentthereof, or a surface of a fuel cell unit, where a reduced level ofthermal insulation can be in contact with, adjacent to, and/or inthermal communication with the face, the segment thereof, or the surfaceof the fuel cell unit, for example, the face, the segment thereof, orthe surface associated with one or more of an afterburner, a fuel cellstack, a reformer and a vaporizer, thereby to increase heat transferthrough and/or from the face, the segment thereof, or the surfaceassociated with the reduced level of insulation. In some embodiments,the methods can include transferring heat preferentially from a face ora surface of a first fuel cell unit; and transferring heatpreferentially from a face or a surface of a second fuel cell unit,where a reduced level of thermal insulation can be in contact with,adjacent to, and/or in thermal communication with the face, the segmentthereof, or the surface of the first fuel cell unit that includes thereduced level of thermal insulation and/or the face, the segmentthereof, or the surface of the second fuel cell unit that includes thereduced level of thermal insulation. A reduced level of insulation canbe associated with the face, segment thereof or surface of one or moreor the reformer, the fuel cell stack, and the afterburner of the firstfuel cell unit and of the second fuel cell unit.

The methods can include transferring heat preferentially from a face ora surface of a first fuel cell unit to a channel between the first fuelcell unit and a second fuel cell unit, and transferring heatpreferentially from a face or a surface of the second fuel cell unit tothe channel.

In certain embodiments, the methods can include transferring heatpreferentially from a face or segment thereof or a surface of a thirdfuel cell unit, where a reduced level of thermal insulation can be incontact with, adjacent to, and/or in thermal communication with the faceor segment thereof, or the surface of the third fuel cell unit, forexample, at least the afterburner of the third fuel cell unit. Inparticular embodiments, a reduced level of thermal insulation can be incontact with, adjacent to, and/or in thermal communication with a secondface or segment thereof or a second surface of the second fuel cellunit, for example, at least the afterburner of the second fuel cellunit. In some embodiments, the first, second and third fuel cell unitscan be arranged linearly, respectively, and the face or segment thereofor the surface of the first fuel cell unit can be opposed the face orsegment thereof or surface of the second fuel cell unit and the secondface or segment thereof or the second surface of the second fuel cellunit can be opposed the face or segment thereof or the surface of thethird fuel cell unit (where the aforementioned “faces,” “segments offaces,” or “surfaces” can be associated with a reduced level of thermalinsulation and as would be understood for other references herein to“faces,” “segments of faces,” or “surfaces” of fuel cell or heaterunit(s) describing other embodiments).

In methods including transferring heat preferentially using a reducedlevel of thermal insulation, one or more of the fuel cell units can bewithin a thermally-regulated zone, where the thermally-regulated zonecan include a temperature-regulating fluid inlet. In such cases,transferring heat preferentially can include deliveringtemperature-regulating fluids through the temperature-regulating fluidinlet of the thermally-regulated zone.

Various methods of the present teachings can include circulatingheat-exchange liquid in thermal communication with one or more of areformer, a fuel cell stack, and an afterburner of a fuel cell unit, topromote heat transfer from one or more of the reformer, the fuel cellstack, and the afterburner to the circulating heat-exchange liquid. Theheat-exchange liquid can include water and/or a glycol. Use of a glycolcan increase the boiling point of the heat-exchange liquid such thatmore heat can be transferred per volume of heat-exchange liquid. Aglycol can include a metal such as nano-sized metal particles toincrease the thermal conductivity of the glycol. The methods ofcirculating heat-exchange liquid can reduce or limit the temperatures ofthe components of a fuel cell unit to limit degradation. For example,the reformer, fuel cell stack and/or afterburner temperatures of anoperating fuel cell unit can be controlled, especially during high fuelflow operating conditions, thereby to limit or reduce the degradation ofthe catalysts and other materials present in those components.

Certain methods of the present teachings can include circulating aheat-exchange liquid in thermal communication with at least one of thefaces or segments thereof or the surfaces of a fuel cell unit, orindependently a first fuel cell unit and/or a second fuel cell unit,where the faces or segments thereof or the surfaces are associated witha reduced level of thermal insulation thereby to transfer heatpreferentially through and/or from the face(s) or segment(s) thereof orthe surface(s) to a heat-exchange liquid.

The methods can include connecting a fuel cell unit to a common liquidheat-exchange conduit of a fuel cell system. The methods of the presentteachings can include transferring heat preferentially from at least oneface or one surface of a fuel cell unit to a circulating heat-exchangeliquid, for example, where a liquid heat-exchange plate or a liquidheat-exchange jacket is in thermal communication with a reduced level ofthermal insulation in contact with, adjacent to, and/or in thermalcommunication with the at least one face or segment thereof or onesurface of the fuel cell unit.

The heated heat-exchange liquid in or exiting a liquid heat-exchangeplate or a liquid heat-exchange jacket can be routed or delivered tovarious devices and/or for a variety of uses as described herein. Forexample, the heated heat-exchange liquid can be routed or delivered to afluid or hydraulic circuit panel, which can direct the heatedheat-exchange liquid to one or more other devices, such as by usingselector valves and the like. Such an arrangement or design canfacilitate efficient liquid-to-liquid heat transfer to a liquid heatsink reservoir such as a water tank. The heated heat-exchange liquid canbe routed or delivered to be in thermal communication with a source ofreformable fuel such a reservoir of liquid reformable fuel or a tank orcontainer of gaseous reformable fuel to preheat the reformable fuel. Forexample, the heated heat-exchange liquid can be used to reduce the heatrequired to vaporize the liquid reformable fuel. The heatedheat-exchange liquid can be routed or delivered to be in thermalcommunication with a tank or container of water to preheat the waterprior to forming or producing steam for use in the operation of a fuelcell unit. In certain embodiments, circulating heated heat-exchangeliquid from a first fuel cell unit towards a second fuel cell unit canreduce the time to initiate chemical reaction or start-up in the secondfuel cell unit in comparison to the time to initiate chemical reactionor start-up in the second fuel cell unit without the benefit of theheated heat-exchange liquid from the first fuel cell unit.

Various methods of the present teachings can include connecting a fuelcell unit to a common (reformable) fuel source conduit of the fuel cellsystem.

Methods of the present teachings can include monitoring and controllingindependently the operations of one or more of a fuel cell system, afuel cell unit, a CHP system, and one or more components thereof,including independently one or more sources of positive gaseouspressure, a reformer, a fuel cell stack, an afterburner, a vaporizer,the various valve assemblies and sensor assemblies associated therewith,and with other components not specifically identified.

It should be understood that where reference is made to a fuel cellunit, its components, configuration and/or operation, the samecomponents, configuration and/or operation can apply to other fuel cellunits of a fuel system, for example, a first fuel cell unit, a secondfuel cell unit, a third fuel cell unit, and so on.

FIG. 1A is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings where a fuelcell unit is within a thermally-shielded zone and the downstream end ofthe exhaust conduit from the afterburner terminates outside of thethermally-shielded zone.

Referring to FIG. 1A, the fuel cell system 100 includes a fuel cell unit102, which includes a reformer 104, a fuel cell stack 106, and anafterburner 108. The fuel cell unit is within a thermally-shielded zone110. The thermally-shielded zone 110 includes one temperature-regulatingfluid inlet 112 and one or more exhaust fluid outlets 114. A source ofpositive gaseous pressure 116 is in operable fluid communication withthe temperature-regulating fluid inlet 112.

The fuel cell system 100 or fuel cell unit 102 includes a cathode airconduit 118 for delivering cathode air through the afterburner 108 to acathode (not shown) of the fuel cell stack 106; an anode reactantsconduit 120 for delivering one or more of anode air, an oxidant, andreformable fuel to the reformer 104 and then to an anode (not shown) ofthe fuel cell stack 106; and an exhaust conduit 122 for exhaustingheated fluids such as heated afterburner combustion products from theafterburner 108. The exhaust conduit 122 includes an upstream end 124 influid communication with the afterburner 108 and a downstream end 126that terminates outside of the thermally-shielded zone 110.

Accordingly, in operation as shown, the source of positive gaseouspressure such as a fan or blower can deliver temperature-regulatingfluid, for example, fresh, ambient air, through thetemperature-regulating fluid inlet and down the fuel cell unit to assistin regulating the temperature of the fuel cell unit and its components.The movement of the temperature-regulating fluid is shown by the arrowsthrough the source of positive gaseous pressure, down the right- andleft-hand sides of the fuel cell unit within the thermally-shielded zoneand out the exhaust fluid outlets on the right- and left-hand side ofthermally-shielded zone near its bottom. As the temperature-regulatingfluid flows through the thermally-shielded zone, the fluid can increasein temperature by the heat generated by the fuel cell unit such thatheated exhaust fluids flowing out of the one or more exhaust fluidoutlets include heated temperature-regulating fluid.

FIG. 1B is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings similar to thefuel cell system of FIG. 1A but where the downstream end of the exhaustconduit from the afterburner terminates within the thermally-shieldedzone. The similar components of figures can be the same or different,for example, having various modifications associated therewith such asmaterials of construction, sensor assemblies, valve configurations,conduit connections and arrangement, and the like.

Referring to FIG. 1B, the fuel cell system 100′ includes a fuel cellunit 102′, which includes a reformer 104′, a fuel cell stack 106′, andan afterburner 108′. The fuel cell unit is within a thermally-shieldedzone 110′. The thermally-shielded zone 110′ includes more than onetemperature-regulating fluid inlet 112′ and one or more exhaust fluidoutlets 114′. A source of positive gaseous pressure 116′ is in operablefluid communication with the plurality of temperature-regulating fluidinlets 112′.

The fuel cell system 100′ or fuel cell unit 102′ includes a cathode airconduit 118′ for delivering cathode air through the afterburner 108′ toa cathode (not shown) of the fuel cell stack 106′; an anode reactantsconduit 120′ for delivering one or more of anode air, an oxidant, andreformable fuel to the reformer 104′ and then to an anode (not shown) ofthe fuel cell stack 106′; and an exhaust conduit 122′ for exhaustingheated fluids such as heated afterburner combustion products from theafterburner 108′. The exhaust conduit 122′ includes an upstream end 124′in fluid communication with the afterburner 108′ and a downstream end126′ that terminates inside of the thermally-shielded zone 110′.

In operation as shown, the source of positive gaseous pressure such as afan or blower can deliver temperature-regulating fluids, for example,fresh, ambient air, through the temperature-regulating fluid inlet anddown the fuel cell unit to assist in regulating the temperature of thefuel cell unit and its components. As the temperature-regulating fluidsflow down the thermally-shielded zone, they can increase in temperatureby the heat generated by the fuel cell unit such that heated exhaustfluids flowing out of the one or more exhaust fluid outlets includeheated temperature-regulating fluids. In addition, the heatedafterburner combustion products are moved downward with the flow of thetemperature-regulating fluids from the source of positive gaseouspressure. The heated afterburner combustion products can increase thetemperature of the temperature-regulating fluids as well as increase thetemperature within the thermally-shielded zone. Consequently, theexhaust from the afterburner can be used efficiently to assist inmaintaining the operating temperature of the fuel cell unit with thetemperature within each thermally-shielded zone being controlled, forexample, in part, by the amount of flow of temperature-regulating fluidsfrom the source of positive gaseous pressure. That is, for example, toreduce the temperature within a thermally-shielded zone and thus, arounda fuel cell unit, the flow of temperature-regulating fluids can beincreased such that the heated fluids within the thermally-shielded zoneare more rapidly expelled or exhausted from the thermally-shielded zonethrough one or more exhaust fluid outlets.

FIG. 1C depicts a schematic diagram of a top view of fuel cell system100″ including four fuel cell units, where each of the fuel cell unitsis within a thermally-shielded zone (as shown and labeled, one fuel cellunit is within a first thermally-shielded zone 110″ and another fuelcell unit is within a second thermally-shielded zone 110′″). Each of thefuel cell units of FIG. 1C is similar to the fuel cell unit shown inFIG. 1B. A source of positive gaseous pressure 116″ is present at thetop of each thermally-shielded zone and the exhaust conduits of the fuelcell units (not shown) terminate within the thermally-shielded zones.However, as depicted in FIG. 1C, the anode reactants conduit 120″ exitsthe thermally-shielded zone 110″ on the opposite side of the cathode airconduit 118″. Such a configuration permits the anode reactants conduit120″ of each fuel cell unit to be connected or coupled to a common(reformable) fuel source conduit 128 via an interface 130. Such anarrangement can beneficially use the heat generated and/or directed tothe channel between the fuel cell units to heat the common fuel sourceconduit and its contents.

FIG. 1D depicts a schematic diagram of a top view of fuel cell system100′″ including four fuel cell units, where each of the fuel cell unitsis within a thermally-shielded zone (as shown and labeled, one fuel cellunit is within a first thermally-shielded zone 110 ^(iv) and anotherfuel cell unit is within a second thermally-shielded zone 110 ^(v)).Each of the fuel cell units of FIG. 1D is similar to the fuel cell unitshown in FIG. 1A. A source of positive gaseous pressure 116′″ is presentat the top of each thermally-shielded zone. The downstream end 126″ ofthe exhaust conduit 122″ terminates outside the thermally-shielded zone110′. The cathode air conduit 118′″ is connected or coupled to a commoncathode air conduit 129 via interface 131. The anode reactants conduit(not shown as hidden in top view by the cathode air conduit) can beconnected or coupled to a common fuel source conduit (also not shown ashidden in top view by the common cathode air conduit). On the oppositeside or across the channel between the fuel cell units, i.e., wherethermally-shielded zone 110 ^(v) is located, another common cathode airconduit 129′ is present, which common cathode air conduit can share thesame fluid stream as or can be independent of the first-described commoncathode air conduit 129. Such an arrangement can separate the thermalexhaust streams from the fuel inlet streams.

FIG. 1E is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings similar toFIG. 1A, but where the fuel cell unit is within a thermally-regulatedzone that has a reduced level of thermal insulation adjacent to asegment of the face of the fuel cell unit having the exhaust conduit.

Referring to FIG. 1E, the fuel cell system 100′ includes a fuel cellunit 102″, which includes a reformer 104″, a fuel cell stack 106″, andan afterburner 108″. The fuel cell unit is within a thermally-regulatedzone 111 (which is the primary difference between the fuel cell systemdepicted in FIG. 1A and the fuel cell system depicted in FIG. 1E). Thethermally-regulated zone 111 includes a reduced level of thermalinsulation 113 adjacent to and in thermal communication with a segmentof a face of the fuel cell unit, which segment includes a face orsurface of the reformer, a face or surface of the fuel cell stack and asegment of the face or surface of the afterburner 108″. Accordingly,heat from the thermally-regulated zone can be preferentially transferredthrough or from those faces, segments, and surfaces in the direction ofthe large arrow labeled “H.” The thermally-regulated zone 111 includesmore than one temperature-regulating fluid inlet 112″ and one or moreexhaust fluid outlets 114″. A source of positive gaseous pressure (ablower) 116 ^(iv) is in operable fluid communication with thetemperature-regulating fluid inlets 112″ via a conduit 117.

The fuel cell system 100 ^(iv) or fuel cell unit 102″ includes a cathodeair conduit 118 ^(iv) for delivering cathode air through the afterburner108″ to a cathode (not shown) of the fuel cell stack 106″; an anodereactants conduit 120—for delivering one or more of anode air, anoxidant, and reformable fuel to the reformer 104″ and then to an anode(not shown) of the fuel cell stack 106″; and an exhaust conduit 122′″for exhausting heated fluids such as heated afterburner combustionproducts from the afterburner 108″. The exhaust conduit 122—includes anupstream end (not labeled) in fluid communication with the afterburner108″ and a downstream end 126—that terminates outside of thethermally-regulated zone 111.

The operation of the fuel cell system shown in FIG. 1E can be similar tothe operation of the fuel cell system depicted in FIG. 1A and describedabove and herein. However, with the presence of a reduced level ofthermal insulation on or adjacent to a face, a segment thereof, or asurface of one or more components of a fuel cell unit, addition heattransfer, management, and control can be achieved. In combination withother features of the present teachings described herein, and inparticular, in relation to the design and arrangement of a plurality offuel cell units of a fuel cell system, heat generated by the fuel cellunits and other components can be used for other purposes to conservethe energy and heat during the operation of a fuel cell system andreduce losses of the same thereby creating more efficiently operatedfuel cell units and fuel cell systems.

FIG. 2A is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 1A but the afterburner,fuel cell stack and reformer are in contact with a liquid heat-exchangejacket.

Referring to FIG. 2A, the fuel cell system 200 includes a fuel cell unit202, which includes a reformer 204, a fuel cell stack 206, and anafterburner 208. The fuel cell unit is within a thermally-shielded zone210. The thermally-shielded zone 210 includes a temperature-regulatingfluid inlet 212 and one or more exhaust fluid outlets 214. A source ofpositive gaseous pressure 216 is in operable fluid communication withthe temperature-regulating fluid inlet 212.

The fuel cell system 200 or fuel cell unit 202 includes a cathode airconduit 218 for delivering cathode air through the afterburner 208 to acathode (not shown) of the fuel cell stack 206; an anode reactantsconduit 220 for delivering one or more of anode air, an oxidant, andreformable fuel to the reformer 204 and then to an anode (not shown) ofthe fuel cell stack 206; and an exhaust conduit 222 for exhaustingheated fluids such as heated afterburner combustion products from theafterburner 208. The exhaust conduit 222 includes an upstream end 224 influid communication with the afterburner 208 and a downstream end 226that terminates outside of the thermally-shielded zone 210.

A liquid heat-exchange jacket 232 is present and in thermalcommunication with the reformer 204, the fuel cell stack 206, and theafterburner 208. The liquid heat-exchange jacket 232 has a liquidheat-exchange outlet 234 and a liquid heat-exchange inlet 236. A liquidheat-exchange jacket typically will encompass and be in thermalcommunication with a perimeter, for example, a circumference, of one ormore components of a fuel cell unit, for example, one or more of theafterburner, the fuel cell stack and the reformer. A liquidheat-exchange plate typically will be present and in thermalcommunication with one or more faces, segments thereof, or surfaces ofone or more components of a fuel cell unit but not completely surroundthe perimeter or circumference, depending on the shape of the fuel cellunit. However, other variations can be used and are included in thepresent teachings, for example, a liquid heat-exchange jacket thatencompasses the entire fuel cell unit (i.e., top, bottom and sides) butfor the conduits and other components into and out of the fuel cellunit.

In operation, a heat-exchange liquid can be delivered through the liquidheat-exchange inlet, circulated through the liquid heat-exchange plateor the liquid heat-exchange jacket to promote heat transfer to theheat-exchange liquid from one or more of the afterburner, the fuel cellstack and the reformer, depending on the thermal communication betweenthe liquid heat-exchange plate or the liquid heat-exchange jacket andthose components of the fuel cell unit. The heated heat-exchange liquidcan be removed from the liquid heat-exchange plate or the liquidheat-exchange jacket via the liquid heat-exchange outlet. The heatedheat-exchange liquid then can be routed to one or more other devicessuch as a liquid-to-liquid heat exchanger, a liquid-to-gas heatexchanger, an air conditioning unit or system, and/or other deviceappropriate for capturing and using or otherwise expelling the heat fromthe heated heat-exchange liquid as described herein or known in the artor otherwise. A heat-exchange liquid can include water and/or a glycol.Use of a glycol can increase the boiling point of the heat-exchangeliquid such that more heat can be transferred per volume ofheat-exchange liquid.

Otherwise, the operation of the fuel cell unit of FIG. 2A is similar tothe operation of the fuel cell unit in FIG. 1A but for the additionalheat transfer capacity provided by the liquid heat-exchange jacket,which can assist in regulating the thermal environment in thethermally-shielded zone, for example, along with the source of positivegaseous pressure in fluid communication with the temperature-regulatingfluid inlet. It should be understood that a liquid heat-exchange plateor a liquid heat-exchange jacket can be used with or be part of a fuelcell unit that is not present within a thermally-shielded zone or athermally-regulated zone. That is, a liquid heat-exchange plate or aliquid heat-exchange jacket can be used independent of athermally-shielded zone and a thermally-regulated zone of the presentteachings. Moreover, if designed and configured appropriately, a liquidheat-exchange jacket can define a thermally-shielded zone or athermally-regulated zone of a fuel cell unit, and/or can be a retainingstructure of a fuel cell unit including any thermal insulation and/orreduced level(s) of thermal insulation, if present.

FIG. 2B is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 1B but the afterburner,fuel cell stack and reformer are in contact with a liquid heat-exchangejacket.

Referring to FIG. 2B, the fuel cell system 200′ includes a fuel cellunit 202′, which includes a reformer 204′, a fuel cell stack 206′, andan afterburner 208′. The fuel cell unit is within a thermally-shieldedzone 210′. The thermally-shielded zone 210′ includes atemperature-regulating fluid inlet 212′ and one or more exhaust fluidoutlets 214′. A source of positive gaseous pressure 216′ is in operablefluid communication with the temperature-regulating fluid inlet 212′.

The fuel cell system 200′ or fuel cell unit 202′ includes a cathode airconduit 218′ for delivering cathode air through the afterburner 208′ toa cathode (not shown) of the fuel cell stack 206′; an anode reactantsconduit 220′ for delivering one or more of anode air, an oxidant, andreformable fuel to the reformer 204′ and then to an anode (not shown) ofthe fuel cell stack 206′; and an exhaust conduit 222′ for exhaustingheated fluids such as heated afterburner combustion products from theafterburner 208′. The exhaust conduit 222′ includes an upstream end 224′in fluid communication with the afterburner 208′ and a downstream end226′ that terminates inside of the thermally-shielded zone 210′.

A liquid heat-exchange plate or a liquid heat-exchange jacket 232′ ispresent and in thermal communication with the reformer 204′, the fuelcell stack 206′, and the afterburner 208′. The liquid heat-exchangejacket 232′ has a liquid heat-exchange outlet 234′ and a liquidheat-exchange inlet 236′. Again, the operation of the fuel cell systemand fuel cell unit depicted in FIG. 2B is similar to the operation ofthe fuel cell unit depicted in FIG. 1B with the addition of the liquidheat-exchange plate or the liquid heat-exchange jacket, whose operationis described herein.

One advantage of the design and arrangement of components in FIG. 2B isthat not only is heat transfer occurring from the exterior faces orsurfaces of the components of the fuel cell unit in contact with oradjacent to the liquid heat-exchange jacket, but also the exhaust fromthe afterburner within the thermally-shielded zone is flowing or beingdelivered or moved over and in contact with the liquid heat-exchangejacket to enhance further the heat transfer from the thermally-shieldedzone to the heat-exchange liquid. Other designs and configurations totake advantage of heat transfer from the exhaust of a fuel cell unit toa heat-exchange liquid are envisioned based on the present teachings,for example, a fuel cell unit within a thermally-regulated zone, or afuel cell unit not present in a thermally-shielded zone or athermally-regulated zone but associated with a liquid heat-exchangeplate or a liquid heat-exchange jacket.

FIG. 2C is a schematic diagram of a side cross-sectional view of anembodiment of a fuel cell system of the present teachings depicting afuel cell unit similar to the one shown in FIG. 2B except only theafterburner and fuel cell stack are in contact with a liquidheat-exchange plate or a liquid heat-exchange jacket where at least twoof the faces of the afterburner and one face of the fuel cell stackinclude a reduced level of thermal insulation for preferential heattransfer to the liquid heat-exchange liquid.

Referring to FIG. 2C, the fuel cell system 200″ includes a fuel cellunit 202″, which includes a reformer 204″, a fuel cell stack 206″, andan afterburner 208″. The fuel cell unit is within a thermally-shieldedzone 210″. The thermally-shielded zone 210″ includes atemperature-regulating fluid inlet 212″ and one or more exhaust fluidoutlets 214″. A source of positive gaseous pressure 216″ is in operablefluid communication with the temperature-regulating fluid inlet 212″.

The fuel cell system 200″ or fuel cell unit 202″ includes a cathode airconduit 218″ for delivering cathode air through the afterburner 208″ toa cathode (not shown) of the fuel cell stack 206″; an anode reactantsconduit 220″ for delivering one or more of anode air, an oxidant, andreformable fuel to the reformer 204″ and then to an anode (not shown) ofthe fuel cell stack 206″; and an exhaust conduit 222″ for exhaustingheated fluids such as heated afterburner combustion products from theafterburner 208″. The exhaust conduit 222″ includes a downstream end226″ that terminates inside of the thermally-shielded zone 210″.

A liquid heat-exchange plate or a liquid heat-exchange jacket 232″ ispresent and in thermal communication with at least two faces or twosurfaces of the reformer 204″ and at least one face or one surface ofthe fuel cell stack 206″. The liquid heat-exchange jacket 232″ has aliquid heat-exchange outlet 234″ and a liquid heat-exchange inlet 236″.

A reduced level of thermal insulation 213 is present along one face ofthe fuel cell unit corresponding to a face or a surface of theafterburner and fuel cell stack (where a reduced level of thermalinsulation is shown by a thinner black line or box vertical along theoutside edges of the fuel cell unit, the black line or box representingthermal insulation generally). A reduced level of thermal insulation213′ also is present along another face or another surface of theafterburner.

Again, the operation of the fuel cell system and fuel cell unit depictedin FIG. 2B is similar to the operation of the fuel cell unit depicted inFIG. 1B with the addition of reduced levels of thermal insulationadjacent to heat generating components of the fuel cell unit and to oneor more liquid heat-exchange plates or jackets, whose operation isdescribed herein.

An advantage of the design and arrangement of components in FIG. 2C isthat preferential heat transfer can occur from the exterior faces orsurfaces of the afterburner and fuel cell stack having a reduced levelof thermal insulation. Accordingly, heat such as radiant heat generatedby the fuel cell stack and the afterburner can be preferentiallytransferred to the heat-exchange liquid in a liquid heat-exchange jacketor liquid heat-exchange plate in contact with or adjacent theretothereby further enhancing the heat transfer from the fuel cell unit andpermitting efficient management of the thermal environment of the fuelcell unit and/or the thermally-shielded zone.

Other designs and configurations to take advantage of preferential heattransfer from a fuel cell unit using reduced levels of thermalinsulation, for example, to a heat-exchange liquid and/or to other fuelcell unit(s), are envisioned based on the present teachings, with otherexamples provided herein.

FIG. 2D depicts a schematic diagram of a top view of fuel cell system200″ including a first fuel cell unit 202″ and a second fuel cell unit202′″. Each of the fuel cell units of FIG. 2C is similar to the fuelcell unit shown in FIG. 1A where, as labeled for the first fuel cellunit, a source of positive gaseous pressure 216″ is present at the topof each thermally-shielded zone 210″ and the exhaust conduit 222″terminates outside of the thermally-shielded zone 210″. However, in thefuel cell units depicted in FIG. 2C, the liquid heat-exchange plate orthe liquid heat-exchange jacket of each fuel cell unit is connected orcoupled to a common liquid heat-exchange conduit system 238.

A common liquid heat-exchange conduit system can include a common liquidheat-exchange inlet conduit to deliver fresh heat-exchange liquid to theliquid heat-exchange plate or the liquid heat-exchange jacket. A commonliquid heat-exchange conduit system can include a common liquidheat-exchange outlet conduit to remove heated heat-exchange liquid fromthe liquid heat-exchange plate or the liquid heat-exchange jacket. Thecommon liquid heat-exchange outlet conduit can be in thermalcommunication with a reservoir of heat-exchange liquid and/or a heatsink for the transfer of the heat from the heated heat-exchange liquidto another solid or fluid medium.

More specifically, again referring to FIG. 2C, the liquid heat-exchangeoutlet 234″ is connected or coupled to a common liquid heat-exchangeoutlet conduit 240 via an outlet interface 242 and the liquidheat-exchange inlet 236″ is coupled to a common liquid heat-exchangeinlet conduit (not shown as it is located under and superimposed by thecommon liquid heat-exchange outlet conduit 240) via an inlet interface244.

FIG. 3 is a schematic diagram of a side cross-sectional view of a fuelcell system of the present teachings where a fuel cell unit includes avaporizer that is within a thermally-shielded zone and the downstreamend of the exhaust conduit from the afterburner terminates within thethermally-shielded zone.

Referring to FIG. 3 , the fuel cell system 300 includes a fuel cell unit302, which includes a reformer 304, a fuel cell stack 306, and anafterburner 308. The fuel cell unit is within a thermally-shielded zone310. The thermally-shielded zone 310 includes temperature-regulatingfluid inlets 312 and one or more exhaust fluid outlets 314. A source ofpositive gaseous pressure 316 is in operable fluid communication withthe temperature-regulating fluid inlets 312.

The fuel cell system 300 or the fuel cell unit 302 includes a vaporizer346 located within the thermally-shielded zone 310. The fuel cell system300 or fuel cell unit 302 includes a cathode air conduit 348 fordelivering cathode air through the afterburner 308 to a cathode (notshown) of the fuel cell stack 306; an anode air conduit 350 fordelivering anode air to the vaporizer 346 and/or reformer 304 and thento an anode (not shown) of the fuel cell stack 306; a reformable fuelconduit 352 for delivering liquid reformable fuel to the vaporizer 346;and an exhaust conduit 322 for exhausting heated fluids such as heatedafterburner combustion products from the afterburner 308. The exhaustconduit 322 depicted terminates inside of the thermally-shielded zone310.

Again, the operation of the fuel cell system and fuel cell unit depictedin FIG. 3 is similar to the operation of the fuel cell units depicted inFIGS. 1B and 2B with the addition of a vaporizer within thethermally-shielded zone and the exclusion of a liquid heat-exchangeplate or a liquid heat-exchange jacket (although a liquid heat-exchangeplate or a liquid heat-exchange jacket can be used with the fuel cellsystem and fuel cell unit depicted in FIG. 3 ). Although the operationof the fuel cell system and fuel cell unit are similar, the inclusion ofa vaporizer within the thermally-shielded zone can increase the use ofthe heat generated by the fuel cell unit, for example, the heat in theexhaust of the afterburner, as the exhaust of the afterburner isdirected towards the vaporizer with the assistance of the source ofpositive gaseous pressure. The heat from the exhaust of the afterburnercan heat (or pre-heat) the anode air before it enters the vaporizer aswell as pre-heating the reformable fuel entering from the bottom of thethermally-shielded zone before the reformable fuel is delivered to thevaporizer. Moreover, the heat generated by the reformer and the fuelcell stack can be used to heat the vaporizer and the various fluidstreams.

FIG. 4A is a schematic diagram of a top view of a CHP system, where fiveexemplary fuel cell units and a heater unit are connected to a commonfuel source conduit and a vaporizer is present in a channel between apair of fuel cell units.

Referring to FIG. 4A, the CHP system 454 includes five fuel cell units402, 402′, 402″, 402′″, 402″″ and a heater unit 456. Each depicted fuelcell unit is substantially the same but for its placement in the fuelcell system, which can represent a “plug and play” fuel cell system inwhich individual fuel cell units and heater units can be removed and/orreplaced with similarly designed and constructed units. For example,each of the anode reactants conduits of the fuel cell units (and aheater unit) is offset from the center of the fuel cell unit butregardless of its position, each fuel cell or heater unit is configuredto be connected or coupled to a common fuel source conduit. Because eachof the fuel cell units is substantially the same, every component orfeature of each one is not labeled.

Still referring to FIG. 4A, one fuel cell unit 402′ has its exhaustconduit 422′ facing into a channel 458 present between a pair of fuelcell units 402′, 402″. Likewise, the other of the pair of fuel cellunits 402″ has its exhaust conduit 422″ facing into the channel 458 andtowards the exhaust conduit 402′ of the first fuel cell unit 402′.Consequently, each fuel cell unit can exhaust heated fluid, and/orpreferentially transfer heat as described herein, from one or more of areformer, a fuel cell stack and an afterburner (not shown here but inFIG. 4B) into a channel 458 present between this pair of fuel cell unitsas well as between the other fuel cell units and heater unit.

Positioned in the channel 458 is a common fuel source conduit 428, whichhas a plurality of interfaces (not shown as hidden in top view by thesources of positive gaseous pressure) to provide operable fluidcommunication between the common fuel source conduit and a reformer ofeach fuel cell unit or a heater unit. Also located in the channel 458 isa vaporizer 446, which can be connected to the common fuel sourceconduit 428 in a variety of configurations depending on the flow ofreformable fuel through the system. As shown, the fuel cell unit 402′has its electronics 460′ located opposite of the channel 458 to wherethe exhaust streams and thus, the heat, from the fuel cell units areexpelled. Such an arrangement can assist the electronics in avoidingexcessively high temperatures that can be generated by a fuel cell unitand fuel cell and CHP systems.

FIG. 4A also includes three sources of positive gaseous pressure 462,462′, 462″ associated with the channel 458 between the pair of fuel cellunits discussed above 402′, 402″. As can be seen for the CHP system, thepairs of adjacent fuel cell units or the adjacent fuel cell unit andheater unit have such sources of positive gaseous pressure present.Although only one source of positive gaseous pressure can be used toeffect directional movement of the heated exhaust from the exhaustconduits, the use of two or three or more positive sources of gaseouspressure between each pair of units permits greater control over theflow of heated exhaust and other fluids within the channels. That is,each source of positive gaseous pressure can be considered to have itsown “zone,” for example, thermal zone, in which it is effective. Eachvertically-defined thermal zone below a source of positive gaseouspressure independently can be monitored and the rate of delivery ofpositive gas pressure in such a thermal zone can controlled asappropriate for each source of positive gaseous pressure.

For example, in the depicted system, the central source of positivegaseous pressure 462′, which is located above the exhaust conduits 422′,422″, may need to deliver more positive gas pressure to drive downwardthe concentrated heat from the exhaust ducts while the peripheralsources of positive gaseous pressure 462, 462″ may not need as strong orhigh of a flow rate of positive gas pressure to maintain a properbalance of the thermal environment within the fuel cell system.

Turning now to FIG. 4B, which is a schematic diagram of a sidecross-sectional view of two exemplary fuel cell units 402′, 402″ of theCHP system 454 of FIG. 4A cut along the line A-A, the source of positivegaseous pressure 462′ can be seen near the top of the channel 458 suchthat it can direct the exhaust from the exhaust outlets 422′, 422″ ofeach fuel cell unit 402′, 402″, respectively. Such an arrangementefficiently can use the heat exhausted from the fuel cell unit to heat avaporizer 446 and common fuel source conduit 428 located in the channel.In addition, the exhaust and heat from one fuel cell unit can be used tosupplement heat to other fuel cell units, heater units, and/orcomponents thereof as needed so that the entire CHP system (or fuel cellsystem) thermally can be managed more efficiently. As a result, thethermal environment in the CHP system (or fuel cell system) can bemonitored and regulated to maintain a constant operating temperature oran appropriate operating temperature for each component or for eachthermal zone of the system.

FIGS. 5A-F are schematic diagrams of top views of various configurationsof fuel cell systems of the present teachings. Each fuel cell unit andits thermal insulation is represented by a square or a rectangle, wherethermal insulation can be distributed about the fuel cell unit andassociated with each face, segment thereof, or surface around theperimeter of the fuel cell unit. (It should be understood that for easeof reference and understanding, the depicted squares and rectangles arereferred to a fuel cell units; however, a fuel cell unit (which could betubular or another cross-sectional shape) would be within the square orrectangle is not necessarily in contact with the thermal insulation asshown.) The fuel cell units can be arranged in arrays to transferpreferentially heat between or among the fuel cell units, where areduced level of thermal insulation is in contact with, adjacent to,and/or in thermal communication with one or more faces, segmentsthereof, or surfaces of the fuel cell unit. A face or surface of a fuelcell unit associated with a reduced level of thermal insulation isrepresented with a thinner line compared to other faces or surfacesrepresented by thicker lines. A reduced level of insulation refers to areduced level of thermal insulation in comparison to thermal insulationin contact with, adjacent to, and/or in thermal communication with theother face(s), segment(s) thereof, and/or other surface(s) of the fuelcell unit.

A reduced level of insulation can be realized by many different designsand materials depending on various considerations such as the shape of afuel cell unit or heater unit and the type of insulation used. Forexample, where a solid thermal insulation includes a sheet or layer ofsolid insulation material that can be positioned around a fuel cellunit, a reduced level of solid thermal insulation can be realized byusing a thinner sheet or layer where preferential heat transfer isdesired. To that end, in certain applications, a reduced level ofthermal insulation can mean no thermal insulation is present. Where afluid thermal insulation is used, for example, a volume of a gas such asair or an air blanket, a reduced level of fluid thermal insulation canbe realized by using a thinner volume of the gas where preferential heattransfer is desired. Moreover, a liquid heat-exchange plate or a liquidheat-exchange jacket can be used in conjunction with the reduced levelof thermal insulation or to provide a reduced level of thermalinsulation where the heat-exchange plate or the liquid heat-exchangejacket can be thinner on one or more faces or surfaces of the fuel cellunit or not present. Combinations of solid thermal insulation and fluidthermal insulation are included in thermal insulation of the presentteachings.

It should be understood that a reduced level of thermal insulation notonly refers to a reduced amount of thermal insulation but also can referto a reduced thermal barrier, or reduced thermal protection orretention. That is, different solid thermal insulation and/or fluidthermal insulation can be used that have different coefficients ofthermal insulation, where a reduced level of thermal insulation canprovide increased thermal transmission (or heat transfer). In otherwords, a similar amount of thermal insulation can be present but havingdifferent levels of thermal transmission and/or thermal conductivitythereby providing a reduce level of thermal insulation.

In addition, a reduced level of thermal insulation can be a grading ofthe thermal insulation along one or more faces or surfaces of a fuelcell unit or thermally-shielded zone or thermally-regulated zone. Forexample, the level of thermal insulation can increase or decrease alongthe direction of a face or a surface of a fuel cell unit from thereformer to the afterburner. A reduced level of thermal insulation canbe present in contact with, adjacent to, and/or in thermal communicationwith a face, or a segment of a face (which can be considered to be asurface) but not the entire face. For example, a reduced level ofthermal insulation can be present in contact with, adjacent to, and/orin thermal communication with one or more of a reformer, a fuel cellstack, and an afterburner such that the segment of the face can be thereformer, the fuel cell stack, the afterburner, the reformer and thefuel cell stack, the reformer and the afterburner, or the fuel cellstack and the afterburner. A reduced level of thermal insulation can bepresent on a segment of a face and can be graded within the segment.

Referring to FIG. 5A, the top view of a square horizontal cross-sectionof a fuel cell unit and its thermal insulation 503 has a thinner linerepresenting a reduced level of thermal insulation on that face, asegment thereof, or surface (which is a “side” in the exemplified squareor rectangular cross-sections) compared to the thermal insulation incontact with, adjacent to, and/or in thermal communication with theother sides of the fuel cell unit represented by the thicker lines. Asshown in FIG. 5A, a reduced level of a thermal insulation, i.e., areduced level of a solid thermal insulation and/or a fluid thermalinsulation, is in contact with, adjacent to, and/or in thermalcommunication with one face, or segment thereof, or one surface of thefuel cell unit. Accordingly, heat can be preferentially transferred awayfrom the fuel cell unit in the direction of the large arrow labeled “H.”

FIG. 5B depicts a first fuel cell unit and its thermal insulation 503and a second fuel cell unit and its thermal insulation 503′, where areduced level of a solid and/or fluid thermal insulation is in contactwith, adjacent to, and/or in thermal communication with one face or onesurface of the first fuel cell unit. As shown, the second fuel cell unitcan be within a thermally-shielded zone or a thermally-regulated zone asno preferential heat transfer occurs from the second fuel cell unit andits thermal insulation 503′.

FIG. 5C depicts a first fuel cell unit and its thermal insulation 503and a second fuel cell unit and its thermal insulation 503″, where areduced level of a solid and/or fluid thermal insulation is in contactwith, adjacent to, and/or in thermal communication with one face or onesurface of the first fuel cell unit and one face or one surface of thesecond fuel cell unit. As shown, the preferential heat transfer canoccur from one fuel cell towards the other fuel cell unit, and viceversa. In such an arrangement, the thermal environments of each fuelcell unit can be maintained with the assistance of heat transfer fromthe other, as and if needed.

FIG. 5D depicts a first fuel cell unit and its thermal insulation 503, asecond fuel cell unit and its thermal insulation 503″, and a third fuelcell unit and its thermal insulation 503′″, in a linear arrangement orarray. As shown, the exterior faces or surfaces (as to the system) ofeach fuel cell unit include thermal insulation. However, a reduced levelof a solid and/or fluid thermal insulation is in contact with, adjacentto, and/or in thermal communication with the interior faces or surfaces(as to the system) of the fuel cell units. Indeed, fuel cell unit andits thermal insulation 503′″ includes two faces or surfaces thatpreferentially can transfer heat to or receive heat from the other fuelcell units.

FIG. 5E depicts a 2×3 array of fuel cell units and their respectivethermal insulation 503 ^(iv), 503 ^(v), 503 ^(vi), 503 ^(ix). Similar tothe 1×3 array shown in FIG. 5D, the exterior faces or surfaces (as tothe system) of each fuel cell unit include thermal insulation. However,a reduced level of a solid and/or fluid thermal insulation is in contactwith, adjacent to, and/or in thermal communication with the interiorfaces or surfaces (as to the system) of the fuel cell units. In thisarrangement, the fuel cell units not only preferentially can transferheat between or among each 1×3 array, but also preferentially cantransfer heat into and across the channel formed by each 1×3 array.

Finally, FIG. 5F depicts another 2×3 array of fuel cell units and theirrespective thermal insulation 503 ^(iv), 503 ^(v), 503 ^(vi), 503^(vii), 503 ^(viii), 503 ^(ix). In this variation, the reduced levels ofthermal insulation are on or adjacent to the exterior faces or surfaces(as to the system) and as well as the interior faces or surfacesadjacent to another fuel cell unit. Accordingly, the heat generated bythe fuel cell units can be preferentially transferred outward and awayfrom the internal channel between each 1×3 array of fuel cell units asshown by the large arrows labeled “H.” Heat also can be preferentiallytransferred between fuel cell units as shown by the smaller arrows. Suchan arrangement can permit the electronics and other heat sensitivecomponents or equipment of the fuel cell system to be present in thechannel (a thermally cooler zone) thereby permitting shorterconnections, for example, for wiring and conduits, to each fuel cellunit.

FIG. 6A is a schematic diagram of a side cross-sectional view of a fuelcell system 600, which includes a fuel cell unit 602 that has a reformer604, a fuel cell stack 606, and an afterburner 608. The fuel cell system600 includes thermal insulation 603, 603′ located in contact with oradjacent to but at least in thermal communication with the components ofthe fuel cell unit including the reformer, fuel cell stack andafterburner. The fuel cell system has reduced levels of thermalinsulation 613, 613′ on or adjacent to but at least in thermalcommunication with segments of two faces of the fuel cell unit 602.

As shown, a segment of a face or surface of a fuel cell unit associatedwith a reduced level of thermal insulation is represented with one linecompared to other segments of a face or surface represented by threelines. The lines can represent sheets of solid thermal insulation suchthat the reduced level of thermal insulation is about two-thirds thinnerthan on or adjacent to other segments of the fuel cell unit. However,the depiction and differences in thickness can represent other forms andlevels of thermal insulation as described herein. As shown, theparticular design and arrangement of the reduced level of thermalinsulation can preferentially transfer heat in the direction of thelarge arrows labeled “H,” for example, away from a face or a surface ofthe fuel cell stack and away from an opposite face or opposite surfaceof the afterburner. Accordingly, thermal management of the fuel cellsystem can be controlled by the placement of reduced levels of thermalinsulation in connection with individual components of a fuel cell unitas well as by the placement of such fuel cell units adjacent to eachother in a fuel cell system.

FIG. 6B is a schematic diagram of a side cross-sectional view of a fuelcell system 600 similar to that shown in FIG. 6A, which includes a fuelcell unit 602 that has a reformer 604, a fuel cell stack 606, and anafterburner 608. The fuel cell system 600 includes a retaining structure633, 633′ such as sheet metal or other rigid thermally conductivematerial that can maintain in place the components of the fuel cell unit602 and adjacent thermal insulation 603″, 603′″. The fuel cell systemhas reduced levels of thermal insulation 613″, 613′″ on or adjacent tobut at least in thermal communication with segments of two faces of thefuel cell unit 602 and more specifically, at least one face or onesurface of the fuel cell stack 606 and at least two faces or twosurfaces of the afterburner.

The fuel cell system also includes one or more liquid heat-exchangejackets or liquid heat-exchange plates 632, 632′ (depending on whetherthe depicted liquid heat-exchange jackets or plates are one unit or twoseparate units). The liquid heat-exchange jackets or liquidheat-exchange plates 632, 632′ are in contact with the outer retainingstructure 633, 633′ of the fuel cell unit 602. The liquid heat-exchangejackets or liquid heat-exchange plates 632, 632′ are adjacent to (via athermally conductive retaining structure) and in thermal communicationwith the faces or the surfaces of the fuel cell stack 606 andafterburner 608 associated with a reduced level of thermal insulation613″, 613′″. Accordingly, heat such as radiant heat generated by thefuel cell stack and the afterburner can be preferentially transferred tothe liquid in the liquid heat-exchange jacket or the liquidheat-exchange plate to assist in the thermal management of the fuel cellunit and fuel cell system.

FIG. 6C is a schematic diagram of a side cross-sectional view of thefuel cell system 600 of FIG. 6B, with the addition of two afterburnerexhaust conduits 622, 622′ in contact with or adjacent to the one ormore liquid heat-exchange plates or liquid heat-exchange jackets for anadditional source of heat for the liquid heat-exchange liquid. Forexample, prior to exhausting and cooling the exhaust from theafterburner, a conduit or other channel can be in contact with oradjacent to but at least in thermal communication with a liquidheat-exchange plate or liquid heat-exchange jacket to provide anothersource of heat to maintain the temperature of the circulating liquidheat-exchange liquid for use as described elsewhere herein or known inthe art.

FIG. 6D is a schematic diagram of a top view of a fuel cell system 600′depicting a rectangular cross-section representing a fuel cell unit andits associated thermal insulation 603, where the thermal insulation isaround the perimeter of the fuel cell unit similar to FIGS. 5A-5F. Thefuel cell system includes a reduced level of thermal insulation on threefaces or surfaces, where the thermal insulation can be absent or at alowest or more reduced level across one face 613′″, and a (moderately)reduced level of thermal insulation is present across two faces 613′,613 ^(v). As shown, an increased amount or level of heat transfer canoccur from the face 613′″ having the lowest level of reduced thermalinsulation as represented by the large arrow labeled with “H,” comparedto the other faces 613 ^(iv), 613 ^(v) having an increased level ofthermal insulation (but still a reduced level of thermal insulation forthe fuel cell unit) as represented by the smaller arrows labeled “H.” Inthis arrangement, the electronics and/or power conditioning components660 of the fuel cell unit are located on or adjacent a face, a segmentthereof, or surface of the fuel cell unit not having a reduced level ofthermal insulation. That is, the electronics, current collection plates,bus bars and other heat-sensitive components can be located orpositioned on or adjacent to a higher level of thermal insulation suchas a thicker amount of solid thermal insulation to shield suchcomponents from heat transfer.

FIG. 7 is a schematic diagram of a top view of a fuel cell system 700having two fuel cell units 702, 702′, each arranged in a horizontaldirection from their respective reformers 704, 704′ to their fuel cellstacks 706, 706′ to their afterburners 708, 708′ where the fuel cellunits share a common fuel source conduit 728 that is connected orcoupled to their respective anode reactants conduits 720, 720′ via avalve assembly 729. Each fuel cell unit has a reduced level of thermalinsulation 713, 713′ on the same face or surface as the exhaust conduits722, 722. Each fuel cell unit also has a reduced level of thermalinsulation 713″, 713′″ between segments of a face or surface of thereformers 704, 704′. Each fuel cell unit includes a cathode air conduit718, 718′. In this arrangement, the heat and exhaust of the fuel cellunits is preferentially transferred in a direction away from theorigination of the common fuel source conduit and the cathode airconduits as shown by the large arrows labeled with “H.” Heat ispreferentially transferred between the fuel cell units as shown by thesmaller arrows labeled with “H.” Such heat transfer can assist inheating and/or maintaining reactants in a vaporized or gaseous state,for example, a reformable fuel such as a liquid reformable fuel.

The present teachings encompass embodiments in other specific formswithout departing from the spirit or essential characteristics thereof.The foregoing embodiments are therefore to be considered in all respectsillustrative rather than limiting on the present teachings describedherein. Scope of the present invention is thus indicated by the appendedclaims rather than by the foregoing description, and all changes thatcome within the meaning and range of equivalency of the claims areintended to be embraced therein.

What is claimed is: 1.-72. (canceled)
 73. A fuel cell system comprisingat least a first fuel cell unit and a second fuel cell unit, whereineach fuel cell unit independently comprises: a reformer; a fuel cellstack in operable fluid communication with the reformer; an afterburnerin operable fluid communication with the fuel cell stack; and an exhaustconduit in thermal and operable fluid communication with theafterburner, wherein the exhaust conduit of each fuel cell unit isconfigured to exhaust heated afterburner combustion products from therespective afterburner to a channel between the first fuel cell unit andthe second fuel cell unit.
 74. The fuel cell system of claim 73, whereinat least one of a vaporizer and a source of liquid is positioned in thechannel.
 75. The fuel cell unit of claim 73, wherein the channel isformed by and between the first fuel cell unit and the second fuel cellunit.
 76. The fuel cell system of claim 73, comprising a source ofpositive gaseous pressure located between the first and the second fuelcell units, and in operable fluid communication with the exhaust streamsfrom each fuel cell unit whereby the exhaust streams can be moved. 77.The fuel cell system of claim 76, further comprising two or more sourcesof positive gaseous pressure in fluid communication with the exhaustconduits and the channel, and configured independently to control thedelivery of exhaust streams from the exhaust conduits into the channel.78. The fuel cell system of claim 73, comprising: a liquid heat-exchangeplate or a liquid heat-exchange jacket in thermal communication with oneor more of the reformer, the fuel cell stack, and the afterburner,independently for the first fuel cell unit and the second fuel cellunit.
 79. A method of thermally managing a fuel cell system, the methodcomprising: exhausting heated fluid from a first fuel cell unit towardsa second fuel cell unit; exhausting heated fluid from the second fuelcell unit towards the first fuel cell unit; and directing the exhaustedheated fluid from the first fuel cell unit and second fuel cell unit toa channel between the first fuel cell unit and the second fuel cellunit.
 80. The method of claim 79, comprising directing the exhaustedheated fluid from the first fuel cell unit and second fuel cell unit toat least one of a vaporizer and a source of liquid positioned in thechannel.
 81. The method of claim 79, wherein the channel is formed byand between the first fuel cell unit and the second fuel cell unit. 82.The method of claim 79, wherein exhausting heated fluid comprisesexhausting independently heated fluid from an afterburner of each of thefirst fuel cell unit and the second fuel cell unit.
 83. The method ofclaim 79, wherein each of the first fuel cell unit and the second fuelcell unit independently is within a thermally-shielded zone.
 84. Themethod of claim 83, wherein exhausting heated fluid comprises exhaustingindependently heated fluid from an afterburner of each of the first fuelcell unit and the second fuel cell unit outside the thermally-shieldedzone of each of the first fuel cell unit and the second fuel cell unit,respectively.
 85. The method of claim 79, wherein the source of fluid isa source of water and the method comprises: heating the water for use insteam reforming.
 86. The method of claim 79, comprising: transferringradiant heat preferentially from a face or a surface of a first fuelcell unit; and transferring radiant heat preferentially from a face or asurface of a second fuel cell unit, wherein a reduced level of a thermalinsulation is in contact with, adjacent to, and/or in thermalcommunication with the face or the surface of the first fuel cell unitand the face or the surface of the second fuel cell unit, thereby toincrease radiant heat transfer from the face or the surface of the firstfuel cell unit and the face or the surface of the second fuel cell unit,wherein a reduced level of thermal insulation is in comparison to thelevel of thermal insulation in contact with, adjacent to, and/or inthermal communication with the other face(s) or other surface(s) of thefirst fuel cell unit and the second fuel cell unit.
 87. The method ofclaim 86, comprising: circulating a heat-exchange liquid independentlyin thermal communication with at least one of the faces or the surfacesof the first fuel cell unit and the second fuel cell unit associatedwith the reduced level of thermal insulation thereby to transfer radiantheat preferentially from the face(s) or the surface(s) to thecirculating heat-exchange liquid.
 88. The method of claim 87, furthercomprising: circulating heated heat-exchange liquid from the first fuelcell unit towards a second fuel cell unit to reduce the time to initiatechemical reaction or start-up in the second fuel cell unit in comparisonto the time to initiate chemical reaction or start-up in the second fuelcell unit without the benefit of the heated heat-exchange liquid fromthe first fuel cell unit.